Power conversion equipment and its control methods, switch driver chips

Abstract

This application provides a power conversion device and its control method, as well as a switch driver chip, relating to the technical field of switch control. The power conversion device includes a controller, a first switch, and a second switch. When the turn-off time of the first switch arrives, the controller provides a first drive current to the gate of the first switch to control a decrease in the gate voltage. When the voltage difference between the first and second switches is greater than or equal to a first threshold, the controller provides a second drive current to the gate of the first switch to control an increase in the gate voltage. When the voltage difference between the first and second switches is greater than or equal to a second threshold, or when the duration of providing the second drive current is greater than or equal to a time threshold, a third drive current is provided to the gate of the first switch to control a decrease in the gate voltage until turn-off. This application can reduce voltage stress and EMI generation, while improving the turn-off speed of the first switch and reducing turn-off losses, making it highly applicable.

Description

Technical Field

[0001] This application relates to the field of switch control technology, specifically to a power conversion device and its control method, and a switch driver chip. Background Technology

[0002] A switching transistor is a power device that exhibits good turn-on and turn-off characteristics under certain conditions. Power conversion equipment can turn the switching transistor on and off by applying a control signal to its control terminal (e.g., the gate). During the turn-off process, the channel current and the channel voltage across the transistor overlap, resulting in turn-off losses.

[0003] Typically, to reduce turn-off losses of switching transistors, power conversion devices can accelerate the turn-off speed of the transistors, thereby shortening the overlap between the channel current and channel voltage, and thus reducing turn-off losses. However, during rapid turn-off, the channel voltage across the transistor changes rapidly, resulting in significant voltage stress across the transistor and amplified noise signals, causing severe electromagnetic interference (EMI) and voltage stress problems. Therefore, how to reduce turn-off losses while simultaneously reducing voltage stress and EMI generated by the transistor is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] This application provides a power conversion device and its control method, as well as a switch driver chip. The power conversion device can reduce voltage stress and EMI generation while improving the turn-off speed of the first switch, thereby reducing turn-off losses and having strong applicability.

[0005] In a first aspect, this application provides a power conversion device, which includes a controller, a first switch and a second switch connected in series; the gate of the first switch is connected to the controller, the first electrode of the first switch is connected to the second switch, and the second electrode of the first switch is grounded or connected to a bus. The controller is configured to: provide a first drive current to the gate of the first switch when the turn-off time of the first switch arrives, so as to control the gate voltage of the first switch to decrease; and provide a second drive current to the gate of the first switch when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a first threshold, so as to control the gate voltage of the first switch to increase; and when the second drive current is provided to the gate of the first switch, provide a third drive current to the gate of the first switch when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a second threshold, or when the duration of providing the second drive current to the gate of the first switch is greater than or equal to a time threshold, so as to control the gate voltage of the first switch to decrease until the first switch is turned off. In this application, when the turn-off time of the first switch arrives, the power conversion device controls the gate voltage of the first switch to decrease through a controller, and controls the gate voltage of the first switch to increase when the voltage difference across the first switch reaches a first threshold, which can effectively reduce voltage stress and EMI generation. Furthermore, when the voltage difference across the first switch reaches a second threshold, or when the duration of the controller providing the second drive current (i.e., the duration of the gate voltage increase of the first switch) reaches a time threshold, the power conversion device controls the gate voltage of the first switch to decrease through a controller until the first switch is completely turned off. This can reduce voltage stress and EMI generation while improving the turn-off speed of the first switch, thereby reducing turn-off losses.

[0006] In conjunction with the first aspect, in a first possible implementation, the controller is configured to: when providing a first drive current to the gate of the first switch, acquire the gate voltage of the first switch, and when the gate voltage of the first switch is less than or equal to a third threshold, provide a fourth drive current to the gate of the first switch, thereby controlling the rate of decrease of the gate voltage of the first switch to be less than a first rate of decrease, where the first rate of decrease is the rate of decrease of the gate voltage of the first switch when the first drive current is provided to the gate of the first switch. In this application, after providing a first drive current to the gate of the first switch, the power conversion device can acquire the gate voltage of the first switch through the controller, and when the gate voltage of the first switch is less than or equal to the third threshold, control the rate of decrease of the gate voltage of the first switch to decrease through the controller, thereby reducing voltage stress and EMI generation while further improving the turn-off speed of the first switch and effectively reducing turn-off losses.

[0007] In conjunction with any of the first aspect to the first possible implementation of the first aspect, in a second possible implementation, the controller is configured to: obtain the magnitude of the first drive current and the magnitude of the third drive current based on the gate drive current used to control the first switch to turn off at a target turn-off speed. In this application, the controller can obtain the magnitudes of the first drive current and the third drive current based on the gate drive current corresponding to the target turn-off speed. Furthermore, when the controller drives the first switch based on the first drive current or the third drive current, the gate voltage of the first switch can drop rapidly, thereby further improving the turn-off speed of the first switch and effectively reducing turn-off losses.

[0008] In a third possible embodiment, in conjunction with any of the first to second possible implementations of the first aspect, the controller is configured to: after providing a first drive current to the gate of the first switch, detect the rate of change of the voltage difference between the first and second electrodes of the first switch, and obtain the magnitude of the second drive current based on the detected rate of change of the voltage difference between the first and second electrodes of the first switch. In this application, when the controller drives the first switch based on the second drive current, the gate voltage of the first switch can be increased to reduce voltage stress and EMI generation. The controller's method of obtaining the magnitude of the second drive current based on the rate of change of the voltage difference between the first and second electrodes of the first switch is easy to implement and highly accurate.

[0009] In a fourth possible embodiment, combining any of the first to second possible implementations of the first aspect, the controller is configured to: after providing a first drive current to the gate of the first switch, detect the time length during which the voltage difference between the first and second electrodes of the first switch increases from a first voltage difference to a second voltage difference, and obtain the magnitude of a second drive current based on the detected time length during which the voltage difference between the first and second electrodes of the first switch increases from the first voltage difference to the second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus. In this application, when the controller drives the first switch based on the second drive current, the gate voltage of the first switch can be increased to reduce voltage stress and EMI generation. The controller's method of obtaining the magnitude of the second drive current based on the time length during which the voltage difference between the first and second electrodes of the first switch increases from the first voltage difference to the second voltage difference is easy to implement and highly accurate.

[0010] In a fifth possible embodiment, in conjunction with any of the first to second possible implementations of the first aspect, the controller is configured to: adjust the magnitude of the second drive current based on the rate of change of the voltage difference between the first and second electrodes of the first switch when a second drive current is provided to the gate of the first switch. In this application, the controller can adjust the magnitude of the second drive current based on the rate of change of the voltage difference between the first and second electrodes of the first switch after providing the second drive current to the first switch, thereby effectively reducing voltage stress and EMI generation, and is easy to implement and can be adjusted in real time.

[0011] In conjunction with any of the first to second possible embodiments of the first aspect, in a sixth possible embodiment, the controller is configured to: when providing a second drive current to the gate of the first switching transistor, adjust the magnitude of the second drive current based on the time length during which the voltage difference between the first and second electrodes of the first switching transistor increases from a first voltage difference to a second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus. In this application, the controller can adjust the magnitude of the second drive current after providing the second drive current to the first switching transistor, based on the time length during which the voltage difference between the first and second electrodes of the first switching transistor increases from a first voltage difference to a second voltage difference, thereby effectively reducing voltage stress and EMI generation. This is easy to implement and can be adjusted in real time.

[0012] In conjunction with any of the first to sixth possible embodiments of the first aspect, in a seventh possible embodiment, the controller is configured to: after providing a first drive current to the gate of the first switch, detect the rate of change of the voltage difference between the first electrode and the second electrode of the first switch, and obtain a time threshold based on the detected rate of change of the voltage difference between the first electrode and the second electrode of the first switch. In this application, the controller can determine the value of the aforementioned time threshold based on the rate of change of the voltage difference between the first electrode and the second electrode of the first switch after providing the first drive current to the first switch, which is easy to implement and has high accuracy.

[0013] In conjunction with any of the first to sixth possible embodiments of the first aspect, in the eighth possible embodiment, the controller is configured to: after providing a first drive current to the gate of the first switch transistor, detect the time length during which the voltage difference between the first electrode and the second electrode of the first switch transistor increases from a first voltage difference to a second voltage difference, and obtain a time threshold based on the detected time length during which the voltage difference between the first electrode and the second electrode of the first switch transistor increases from the first voltage difference to the second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus. In this application, the controller can determine the value of the aforementioned time threshold based on the time length during which the voltage difference between the first electrode and the second electrode of the first switch transistor increases from the first voltage difference to the second voltage difference after providing the first drive current to the first switch transistor, which is easy to implement and has high accuracy.

[0014] In conjunction with any of the first to eighth possible embodiments of the first aspect, in the ninth possible embodiment, the controller is configured to: when the turn-on time of the first switch arrives, provide a fifth drive current to the gate of the first switch to control the gate voltage of the first switch to rise; and when the gate voltage of the first switch is greater than or equal to a fourth threshold, provide a sixth drive current to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be less than a first rise rate, the first rise rate being the rise rate of the gate voltage of the first switch when the fifth drive current is provided to the gate of the first switch; when the sixth drive current is provided to the gate of the first switch, when the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to the fifth threshold, provide a seventh drive current to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be greater than a second rise rate, until the first switch is turned on; wherein, the second rise rate is the rise rate of the gate voltage of the first switch when the sixth drive current is provided to the gate of the first switch, and the fifth threshold is less than the operating voltage of the bus. In this application, when the first switch is turned on, the power conversion device controls the gate voltage of the first switch to rise via a controller. When the gate voltage of the first switch is greater than or equal to a fourth threshold, the device controls the rate of increase of the gate voltage to decrease, effectively reducing current stress and EMI generation. Furthermore, when the voltage difference across the first switch is less than or equal to a fifth threshold, the power conversion device controls the rate of increase of the gate voltage of the first switch to increase via a controller until the first switch is fully turned on. This reduces current stress and EMI generation while increasing the turn-on speed of the first switch, thereby reducing conduction losses.

[0015] In conjunction with the ninth possible implementation of the first aspect, in the tenth possible implementation, the controller is configured to: obtain the magnitudes of the fifth drive current and the seventh drive current based on the gate drive current used to control the first switch to turn on at a target turn-on speed. In this application, the controller can obtain the magnitudes of the fifth drive current and the seventh drive current based on the gate drive current corresponding to the target turn-on speed. Furthermore, when the controller drives the first switch based on the fifth drive current or the seventh drive current, the gate voltage of the first switch can rise rapidly, thereby further improving the turn-on speed of the first switch and effectively reducing turn-off losses.

[0016] Secondly, this application also provides a control method for a power conversion device, the power conversion device including a first switch and a second switch connected in series; the first electrode of the first switch is connected to the second switch, and the second electrode of the first switch is grounded or connected to a bus. The method includes: when the turn-off time of the first switch arrives, providing a first drive current to the gate of the first switch to control the gate voltage of the first switch to decrease; and when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a first threshold, providing a second drive current to the gate of the first switch to control the gate voltage of the first switch to increase; when the second drive current is provided to the gate of the first switch, when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a second threshold, or when the duration of providing the second drive current to the gate of the first switch is greater than or equal to a time threshold, providing a third drive current to the gate of the first switch to control the gate voltage of the first switch to decrease until the first switch is turned off.

[0017] In conjunction with the second aspect, in a first possible implementation, the method further includes: when providing a first drive current to the gate of the first switch, acquiring the gate voltage of the first switch, and when the gate voltage of the first switch is less than or equal to a third threshold, providing a fourth drive current to the gate of the first switch, so as to control the rate of decrease of the gate voltage of the first switch to be less than a first rate of decrease, wherein the first rate of decrease is the rate of decrease of the gate voltage of the first switch when the first drive current is provided to the gate of the first switch.

[0018] In conjunction with any of the second aspect to the first possible implementation of the second aspect, in the second possible implementation, the method includes: obtaining the magnitude of a first drive current and the magnitude of a third drive current based on the gate drive current used to control the first switch to turn off at a target turn-off speed.

[0019] In conjunction with any of the second aspect to the second possible implementation, in a third possible implementation, the method includes: after providing a first drive current to the gate of a first switch, detecting the rate of change of the voltage difference between a first electrode and a second electrode of the first switch, and obtaining the magnitude of a second drive current based on the detected rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

[0020] In conjunction with any of the second aspect to the second possible implementation, in a fourth possible implementation, the method includes: after providing a first drive current to the gate of a first switch, detecting the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from a first voltage difference to a second voltage difference, and obtaining the magnitude of a second drive current based on the detected time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

[0021] In conjunction with any of the second aspect to the second possible implementation, in the fifth possible implementation, the method includes: adjusting the magnitude of the second drive current based on the rate of change of the voltage difference between the first electrode and the second electrode of the first switch when a second drive current is provided to the gate of the first switch.

[0022] In conjunction with any of the second aspect to the second possible implementation, in the sixth possible implementation, the method includes: when providing a second drive current to the gate of the first switch, adjusting the magnitude of the second drive current based on the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from a first voltage difference to a second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

[0023] In conjunction with any of the second aspect to the sixth possible implementation of the second aspect, in the seventh possible implementation, the method includes: after providing a first drive current to the gate of the first switch, detecting the rate of change of the voltage difference between the first electrode and the second electrode of the first switch, and obtaining a time threshold based on the detected rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

[0024] In conjunction with any of the second to sixth possible embodiments of the second aspect, in the eighth possible embodiment, the method includes: after providing a first drive current to the gate of the first switch, detecting the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from a first voltage difference to a second voltage difference, and obtaining a time threshold based on the detected time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

[0025] In conjunction with any of the second to eighth possible embodiments of the second aspect, in the ninth possible embodiment, the method includes: when the turn-on time of the first switch arrives, providing a fifth drive current to the gate of the first switch to control the gate voltage of the first switch to rise; and when the gate voltage of the first switch is greater than or equal to a fourth threshold, providing a sixth drive current to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be less than a first rise rate, the first rise rate being the rise rate of the gate voltage of the first switch when the fifth drive current is provided to the gate of the first switch; when the sixth drive current is provided to the gate of the first switch, when the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to the fifth threshold, providing a seventh drive current to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be greater than a second rise rate, until the first switch is turned on; wherein, the second rise rate is the rise rate of the gate voltage of the first switch when the sixth drive current is provided to the gate of the first switch, and the fifth threshold is less than the operating voltage of the bus.

[0026] In conjunction with the ninth possible implementation of the second aspect, in the tenth possible implementation, the method includes: obtaining the magnitude of the fifth drive current and the magnitude of the seventh drive current based on the gate drive current used to control the first switch to turn on at a target turn-on speed.

[0027] In conjunction with the second possible implementation of the second aspect, in the eleventh possible implementation, the method further includes: obtaining multiple voltage thresholds based on the operating voltage of the bus, wherein the voltage thresholds are less than the operating voltage of the bus; when a sixth drive current is provided to the gate of the first switch, traversing the multiple voltage thresholds to use each voltage threshold as a candidate voltage threshold, and when the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to the candidate voltage threshold, providing a seventh drive current to the gate of the first switch to control the gate voltage of the first switch to rise until the first switch is turned on; obtaining the current amplitude of the first electrode and the second electrode corresponding to the candidate voltage threshold during the turn-on process of the first switch, so as to obtain the current amplitude of the first electrode and the second electrode corresponding to each voltage threshold; and determining a fifth threshold from the multiple voltage thresholds based on the current amplitude of the first electrode and the second electrode corresponding to each voltage threshold.

[0028] Thirdly, this application provides a switch driver chip, which includes the controller described in the first aspect of this application and any possible embodiment thereof. The switch driver chip is connected to a first switch transistor and a second switch transistor. The switch driver chip is used to drive the first switch transistor to turn on or off, and to drive the second switch transistor to turn on or off. The beneficial effects of the solutions provided in the second and third aspects can be referred to the description in the first aspect above, and will not be repeated here. Attached Figure Description

[0029] Figure 1 A schematic diagram of the Buck converter provided in the embodiments of this application;

[0030] Figure 2 This is a schematic diagram of a signal waveform of a switching transistor provided in an embodiment of this application;

[0031] Figure 3 This is another signal waveform diagram of the switching transistor provided in an embodiment of this application;

[0032] Figure 4 A schematic diagram of the frame of the power conversion device provided in the embodiments of this application;

[0033] Figure 5 A waveform diagram of the first switching transistor provided in an embodiment of this application;

[0034] Figure 6 Another waveform diagram of the first switching transistor provided in the embodiments of this application;

[0035] Figure 7 Another waveform diagram of the first switching transistor provided in an embodiment of this application;

[0036] Figure 8A schematic flowchart of the control method for the power conversion device provided in this application. Detailed Implementation

[0037] The power conversion device provided in this application is applicable to various application scenarios, such as switching power supplies, secondary power supplies, and tertiary power supplies. The power conversion device includes a first and second switch connected in series, which can be understood as a bridge topology circuit. When the power conversion device is used in a switching power supply scenario, depending on the topology connected to the first and second switches, the power conversion device can specifically be a boost converter, a buck converter, a buck-boost converter, or a resonant converter, etc. In this case, the first and second switches can be a half-bridge topology circuit in a boost converter or a buck converter, or one arm of a full-bridge topology circuit in a buck-boost converter or a resonant converter. For ease of understanding, the following description uses a buck converter as an example to illustrate the power conversion device provided in this application.

[0038] In some feasible implementations, when the power conversion device provided in this application embodiment is a Buck converter, the structure of the power conversion device can be as follows: Figure 1 As shown. For details, please refer to [link / reference]. Figure 1 , Figure 1 This is a schematic diagram of the Buck converter provided in an embodiment of this application.

[0039] Figure 1 The Buck converter 100 shown includes a first switch Q1, a second switch Q2, a first capacitor C1, and a first inductor L1. The first switch Q1 and the second switch Q2 are connected in series at a first connection point to form a half-bridge switching circuit. One end of the first inductor L1 is connected to the first connection point, and the other end is grounded through the first capacitor C1. The first capacitor C1 is connected in parallel with the load.

[0040] In this configuration, the first switch Q1 is connected in series between the first connection point and the ground wire, and the second switch Q2 is connected in series between the first connection point and the power supply. Alternatively, in other applications, the first switch Q1 can be connected in series between the first connection point and the power supply, and the second switch Q2 can be connected in series between the first connection point and the ground wire. Figure 1 The positions of the first switch Q1 and the second switch Q2 shown can be interchanged, and this application embodiment does not limit this.

[0041] It is understood that the description of the internal structure of the Buck converter 100 in this application embodiment is only an example of a power conversion device. In other application scenarios, the internal structure of the power conversion device will be different depending on the function of the power conversion device.

[0042] It should be noted that the type of switching transistor in the embodiments of this application can be, but is not limited to, Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), Insulated-Gate Bipolar Transistor (IGBT), and SiC power transistor, etc. Specifically, the switching transistor can include a first electrode, a second electrode, and a control electrode. The power conversion device can control the switching transistor to be turned on or off through the control electrode. When the power conversion device controls the switching transistor to be turned on, current can be transferred between the first electrode and the second electrode of the switching transistor. When the power conversion device controls the switching transistor to be turned off, current cannot be transferred between the first electrode and the second electrode of the switching transistor. Taking a MOSFET as an example, the control electrode of the switching transistor is the gate, the first electrode of the switching transistor can be the source, and the second electrode can be the drain, or the first electrode can be the drain and the second electrode can be the source. Taking an IGBT as an example, the control electrode of the switching transistor is the gate, the first electrode of the switching transistor can be the collector, and the second electrode can be the emitter, or the first electrode can be the emitter and the second electrode can be the collector.

[0043] The Buck converter 100 also includes a controller. This controller controls the first switch Q1 and the second switch Q2 to alternately turn on and off, thereby controlling the half-bridge switching circuit to switch to different operating states and causing the first inductor L1 and the first capacitor C1 to charge or freewheel, thus providing a DC voltage Vout to the load. The DC voltage Vout output by the Buck converter 100 is lower than the input power supply voltage Vbus, meaning the Buck converter 100 can perform step-down conversion to convert the power supply voltage Vbus into the operating voltage required by the load and provide it to the load.

[0044] For example, in a power grid system, when the AC power grid is connected to the equipment room and supplies power, the supply voltage is typically medium voltage (e.g., 10kV) AC, while the load's operating voltage is typically low voltage (e.g., 220V or 400V) DC or AC. Therefore, the power grid system can be equipped with a Buck converter 100 to step down the voltage connected to the AC power grid to provide the required voltage magnitude and type to the load.

[0045] It should be noted that the power supply connected to the Buck converter 100 can be either a DC power supply or an AC power supply (such as the AC mains power mentioned above). The load connected to the Buck converter 100 can be a device powered by either DC or AC. When the power supply is DC and the load is a device powered by DC, the Buck converter 100 has both connection and voltage conversion functions. When the power supply is AC and the load is a device powered by DC, the Buck converter 100 also has a rectification function.

[0046] Understandably, as a crucial component required for the operation of the Buck converter 100, the turn-on and turn-off processes of the first switch Q1 or the second switch Q2 will affect the overall efficiency and performance of the power conversion device.

[0047] In some feasible implementations, the turn-off speed of the first switch Q1 or the second switch Q2 affects the generation of turn-off losses. Specifically, during the turn-off process of the first switch Q1 or the second switch Q2, due to the presence of parasitic capacitance, the current flowing through the first switch Q1 or the second switch Q2 cannot immediately drop to zero, while the voltage across the first switch Q1 or the second switch Q2 has already increased. This results in voltage and current overlap across the first switch Q1 or the second switch Q2, thus causing turn-off losses. For example, the voltage and current changes during the turn-off of the first switch Q1 or the second switch Q2 can be found in [reference needed]. Figure 2 As shown, Figure 2 This is a schematic diagram of a signal waveform of a switching transistor provided in an embodiment of this application. Figure 2 The Ic shown represents the current magnitude of the first switch Q1 or the second switch Q2, and Vq represents the voltage magnitude of the first switch Q1 or the second switch Q2. Figure 2 It can be seen that as the current Ic of the first switch Q1 or the second switch Q2 decreases, the voltage Vq increases, thus creating a shadowed region of overlapping voltage and current when the first switch Q1 or the second switch Q2 is turned off. This is understandable. Figure 2 The larger the area of ​​the shaded region formed by the overlap of voltages Vq and Ic, the greater the turn-off loss of the first switch Q1 or the second switch Q2.

[0048] Similarly, the conduction losses generated by the first switch Q1 or the second switch Q2 during the conduction process can be referred to the specific implementation of the above-described turn-off process, and will not be repeated here in the embodiments of this application.

[0049] Understandably, the Buck converter 100, by accelerating the turn-off speed of the first switch Q1 or the second switch Q2 through the controller, can reduce the overlap of voltage and current during the turn-off of the first switch Q1 or the second switch Q2, i.e. Figure 2 The area of ​​the shaded region shown is reduced, which in turn reduces the turn-off loss of the first switch Q1 or the second switch Q2.

[0050] Furthermore, the turn-off speed of either the first switch Q1 or the second switch Q2 affects the generation of voltage stress. Specifically, when the first switch Q1 or the second switch Q2 is turned off, the midpoint voltage between them suddenly changes, causing a sudden increase or decrease in the voltage across either switch Q1 or Q2. This generates extremely high voltage spike stress, i.e., voltage stress. Excessive voltage stress can damage the first switch Q1 or the second switch Q2, shortening their lifespan. Simultaneously, significant voltage stress can also cause EMI problems. Therefore, while accelerating the turn-off speed can reduce turn-off losses, this also leads to greater voltage stress in the first switch Q1 or the second switch Q2, and amplifies noise signals, causing severe EMI and voltage stress problems, thus affecting the stable operation of the Buck converter 100.

[0051] Similarly, the conduction losses, current stress, and EMI generated during the conduction process of the first switch Q1 or the second switch Q2 can be referred to the specific implementation of the above-described turn-off process, and will not be repeated here in the embodiments of this application.

[0052] To facilitate understanding of the principles underlying the losses, voltage stress, and EMI generated by the first switch Q1 and the second switch Q2, the following description first illustrates the operating characteristics of the first switch Q1 when it is off and on. The operating characteristics of the second switch Q2 when it is off and on can be found in the description of the first switch Q1; these will not be repeated here in the embodiments of this application.

[0053] In some feasible implementations, taking the first switch Q1 as a MOSFET as an example, combined with... Figure 1 and Figure 3 The conduction process of the first switching transistor Q1 will be explained. Figure 3 This is another signal waveform diagram of the switching transistor provided in an embodiment of this application. (See diagram below.) Figure 3 As shown, after the controller receives a high-level pulse width modulation (PWM) signal to control the conduction of the first switch Q1, the conduction process of the first switch Q1 can be divided into the following four stages:

[0054] In the first stage, t0 to t1, after receiving a high-level PWM signal, the controller outputs a drive current Ig to the gate of the first switch Q1. This drive current charges the parasitic capacitance Cgs between the gate and source of the first switch Q1. Since the first switch Q1 is not turned on, the current Ic flowing through it and the voltage Vq across it remain constant. When the voltage across the parasitic capacitance Cgs increases from V0 to V1, the first switch Q1 meets the turn-on condition and enters the second stage, t1-t2.

[0055] In the second stage, from t1 to t2, the first switching transistor Q1 begins to conduct, and the current Ic flowing through it gradually increases. At this time, the change in current Ic causes a voltage change in the parasitic inductance of the first switching transistor Q1. The faster the switching transistor Q1 turns on, the greater the change in current Ic, and consequently, the greater the voltage change caused by its parasitic inductance. Therefore, the first switching transistor Q1 enters a stage with relatively high current stress during the second stage. When the current Ic reaches its maximum value, the third stage, t2-t3, begins. During this period, the gate voltage Vg of the first switching transistor Q1 increases to V2.

[0056] In the third stage, from t2 to t3, the first switch Q1 enters the voltage drop phase, which is also the Miller plateau phase. The first switch Q1 is not yet fully turned on, and the voltage Vq across it drops rapidly. At this time, the change in voltage Vq across the first switch Q1 affects its conduction loss. When the gate voltage Vg rises from V2 to V3, the fourth stage, t3-t4, begins.

[0057] In the fourth stage, from t3 to t4, the driving current continues to charge the parasitic capacitance Cgs of the first switch Q1 until the parasitic capacitance Cgs is charged to the maximum voltage. At this time, the gate voltage Vg of the first switch Q1 rises to the conduction threshold V4, the conduction degree of the first switch Q1 is at its maximum and the internal resistance is at its minimum, and the conduction process of the first switch Q1 ends.

[0058] As can be seen from the conduction process of the first switch Q1 described above, the current Ic continuously changes in the second stage, and the voltage Vq continuously changes in the third stage. The shorter the conduction process of the first switch Q1, the lower its conduction loss, and consequently, the shorter the duration of the second and third stages. When the duration of the second and third stages is shortened, the rate of change of current Ic in the second stage increases, and the rate of change of voltage Vq in the third stage increases. These rapid changes in current and voltage enhance noise signals, causing serious EMI and current stress problems.

[0059] In some feasible implementations, such as Figure 3 As shown, after the controller receives a low-level PWM signal to control the first switch Q1 to turn on, the turn-off process of the first switch Q1 can be divided into the following four stages;

[0060] In the fifth stage, from t5 to t6, the controller stops outputting the drive current Ig to the first switch Q1, causing the gate voltage Vg of the first switch Q1 to decrease from its maximum value V5. During this stage, the first switch Q1 is not yet turned off, and so on... Figure 3 As shown, the channel current Ic of the first switch Q1, i.e., the current flowing through the first switch Q1, remains unchanged. Simultaneously, the voltage Vq across the first switch Q1 also remains relatively stable. During the fifth stage, the controller can rapidly pull down the gate voltage Vg of the first switch Q1 to reduce the turn-off delay and minimize losses caused by increased internal resistance during this period. In other words, during the fifth stage, the turn-off speed of the first switch Q1 is directly proportional to the magnitude of the drive current Ic. Furthermore, when the gate voltage Vg of the first switch Q1 decreases from its maximum value V5 to V6, the turn-off of the first switch Q1 enters the sixth stage.

[0061] In the sixth stage, from t6 to t7, the first switch Q1 enters the Miller plateau stage, and its current Ic remains approximately constant. The first switch Q1 begins to turn off, and the voltage Vq across it increases accordingly. At this time, the drive current Ig provided by the controller to the first switch Q1 affects the rate of change of the voltage Vq across it. Specifically, the larger the drive current Ig provided by the controller, the faster the rate of change of the voltage Vsw at the midpoint between the first switch Q1 and the second switch Q2, and thus the faster the rate of change of the voltage Vq across the first switch Q1. A larger drive current Ig can correspondingly accelerate the turn-off speed of the first switch Q1, but it will increase the EMI and voltage stress of the first switch Q1. In other words, in the sixth stage, the voltage stress and EMI generated by the first switch Q1 are inversely proportional to its turn-off speed. Furthermore, when the gate voltage Vg of the first switch Q1 decreases from V6 to V7, the turn-off of the first switch Q1 enters the seventh stage.

[0062] In the seventh stage, from t7 to t8, the first switch Q1 enters the current-off phase. The current Ic of the first switch Q1 begins to decrease, and as the current Ic decreases, the voltage Vq across the first switch Q1 also decreases. At this time, the drive current Ig provided by the controller to the first switch Q1 has a significant impact on the current Ic of the first switch Q1. Specifically, the larger the drive current Ig provided by the controller, the larger the gate voltage Vg of the first switch Q1, and the faster the rate of change of the current Ic of the first switch Q1. The faster the rate of change of the current Ic of the first switch Q1, the greater the voltage stress on the first switch Q1. That is to say, in the seventh stage, the voltage stress generated by the first switch Q1 is inversely proportional to the turn-off speed of the first switch Q1. Furthermore, when the gate voltage Vg of the first switch Q1 decreases from the voltage value V7 to V8, the turn-off of the first switch Q1 enters the eighth stage.

[0063] In the eighth stage, from t8 to t9, the first switch Q1 enters the current cutoff stage, meaning its current Ic has decreased to a negligible level. At this time, the controller can rapidly pull down the gate voltage Vg of the first switch Q1 to reduce its turn-off delay. The gate voltage Vg continues to decrease until it reaches V9, at which point the turn-off process of the first switch Q1 is complete. Here, V9 represents the turn-off threshold voltage of the first switch; therefore, when the gate voltage Vg of the first switch Q1 drops to V9, the first switch Q1 is completely turned off.

[0064] Therefore, the Buck converter 100 provided in this application embodiment controls the first switch Q1 and the second switch Q2 to turn off or on through the controller, which can reduce the losses of the first switch Q1 and the second switch Q2 during the turn-off or turn-on process. At the same time, it reduces the generated EMI, voltage stress and current stress, which can extend the service life of the first switch Q1 and the second switch Q2 and improve the overall efficiency and working performance of the Buck converter 100.

[0065] The above are merely examples of application scenarios for the power conversion device provided in this application, and are not exhaustive. This application does not limit the application scenarios.

[0066] As can be seen from the above, the power conversion device provided in this application controls the turn-on and turn-off processes of the first and second switching transistors through a controller, which can reduce losses while improving EMI and voltage stress issues. For ease of understanding, the following will be combined with... Figures 4 to 7 The working principle of the controller in the power conversion device provided in this application is illustrated by an example.

[0067] In some feasible implementations, the first and second switching transistors in the power conversion device are connected in series. The other end of the connection between the first and second switching transistors can be grounded, and the other end of the connection between the second and first switching transistors can be connected to a bus to receive the bus voltage. This bus is the bus in the power conversion device, providing the operating voltage required for the operation of each electronic component. Alternatively, the other end of the connection between the first and second switching transistors can be connected to the bus to receive the bus voltage, and the other end of the connection between the second and first switching transistors can be grounded. In other words, the positions of the first and second switching transistors can be interchanged in the embodiments of this application, and this application does not limit this.

[0068] Specifically, the controller can connect to the gate of the first switching transistor via a current control terminal to provide a drive current to the gate of the first switching transistor, thereby controlling the first switching transistor to turn on or off. Simultaneously, the controller can connect to the first electrode of the first switching transistor via a first voltage detection terminal to obtain the voltage magnitude of the first electrode of the first switching transistor. Furthermore, based on the obtained voltage magnitude of the first electrode of the first switching transistor, the controller can determine the voltage difference between the first electrode and the second electrode of the first switching transistor.

[0069] It is understood that, in this embodiment of the application, taking a MOS transistor as the first switching transistor, the first electrode and the second electrode can be the source and drain of the first switching transistor, respectively. The first electrode can be the source and the second electrode can be the drain, or the first electrode can be the drain and the second electrode can be the source; this embodiment of the application does not limit this.

[0070] For example, such as Figure 4 As shown, Figure 4 This is a schematic diagram of a power conversion device provided in an embodiment of this application. Figure 4 The power conversion device 400 shown includes a controller 410, a first switch Q1, and a second switch Q2. The controller 410 is connected to the gate of the first switch Q1 via a current control terminal and to the first electrode of the first switch Q1 via a first voltage detection terminal to acquire the voltage of the first electrode of the first switch Q1. The first electrode of the first switch Q1 is connected to the second switch Q2, and the other end of the second switch Q2 connected to the first switch Q1 is connected to a bus. The second electrode of the first switch Q1 is grounded.

[0071] It should be noted that the power conversion device may also include various other electronic components to support the implementation of the functions, such as filtering units and rectifier units, which will not be described in detail in the embodiments of this application. In other application scenarios, the product form and internal circuit structure of the power conversion device can be adjusted according to actual needs.

[0072] Furthermore, as an electronic component in the power conversion device, the controller is connected to the aforementioned bus and ground terminal within the power conversion device, and the second electrode of the first switching transistor is also connected to the ground terminal. This means the controller can obtain the voltage magnitude between the first and second electrodes of the first switching transistor. Therefore, the controller can connect to the first electrode of the first switching transistor via its first voltage detection terminal to obtain the voltage magnitude of the first electrode, and thus determine the voltage magnitude between the first and second electrodes of the first switching transistor.

[0073] In some feasible implementations, the controller can also obtain the voltage between the first and second electrodes of the first switching transistor via an external detection device. This detection device can be connected to the first and second electrodes of the first switching transistor and send the detected voltage levels of the first and second electrodes to the controller. The controller can then obtain the voltage between the first and second electrodes of the first switching transistor based on the received voltage levels. It should be noted that the above are merely examples, and the embodiments of this application do not limit the specific implementation method by which the controller obtains the voltage between the first and second electrodes of the first switching transistor.

[0074] For example, such as Figure 4 As shown, the controller 410 can obtain the voltage magnitude of the first electrode of the first switching transistor Q1 through the first voltage detection terminal. Assuming the controller 410 obtains a voltage of Vx at the first electrode of the first switching transistor Q1, and since the second electrode is grounded, the controller can determine that the voltage difference between the first and second electrodes of the first switching transistor Q1 is equal to Vx - 0. Alternatively, if the second electrode of the first switching transistor Q1 is connected to a bus, and the operating voltage of the bus is Vy, the controller can determine that the voltage difference between the first and second electrodes of the first switching transistor Q1 is equal to Vx - Vy. The above description is merely an example and does not constitute a limitation on the embodiments of this application.

[0075] It is understood that the controller in the power conversion device can control the first and second switching transistors to alternately turn on and off, so that the power conversion device can operate and provide the operating voltage to the load. For ease of explanation, the following description will take the controller controlling the first switching transistor to turn off and on as an example. The implementation method of the controller controlling the second switching transistor to turn off and on can be referred to the relevant description of the first switching transistor, and will not be repeated in this embodiment.

[0076] In some feasible implementations, the principle of the controller controlling the first switch to turn off will be introduced first.

[0077] As can be seen from the above, the first switching transistor has different operating characteristics at different stages of the turn-off process. For example, as... Figure 3As shown, in the fifth stage, the rapid turn-off of the first switch does not lead to EMI or voltage stress, while in the sixth stage, a rapid turn-off of the first switch directly leads to EMI and voltage stress. Therefore, in order to reduce voltage stress and EMI while reducing the turn-off loss of the first switch, the power conversion device provided in this application embodiment can perform segmented control of the turn-off process of the first switch according to the operating characteristics of the first switch at different stages. That is, different control methods are applied to the first switch at different stages, thereby simultaneously reducing the turn-off speed, voltage stress, and EMI of the first switch.

[0078] Specifically, when the controller receives a low-level PWM signal for controlling the first switching transistor, it indicates that the first switching transistor is about to turn off. At this time, the first switching transistor switches from the on state to the off state. The controller can first provide a first drive current to the gate of the first switching transistor to control the gate voltage of the first switching transistor to decrease.

[0079] It should be noted that the controller can control the voltage increase or decrease of the gate voltage of the first switch by providing a drive current (such as the first drive current mentioned above) to the gate of the first switch. Specifically, the first switch is fully turned on when its gate voltage is greater than or equal to a turn-on threshold. This turn-on threshold can be understood as the minimum gate voltage required for the first switch to be fully turned on; that is, the first switch is not fully turned on when its gate voltage is less than this threshold. Therefore, when controlling the first switch to turn on, the controller needs to pull its gate voltage up to a range greater than or equal to the turn-on threshold. Similarly, the first switch is fully turned off when its gate voltage is less than or equal to a turn-off threshold. This turn-off threshold can be understood as the maximum gate voltage required for the first switch to be fully turned off; that is, the first switch is not fully turned off when its gate voltage is greater than this threshold. Therefore, when controlling the first switch to turn off, the controller needs to pull its gate voltage down to a range less than or equal to the turn-off threshold. The specific values ​​of the turn-off threshold and turn-on threshold can be flexibly adjusted for different types of first switching transistors, and this application embodiment does not limit this.

[0080] Since the turn-on threshold of the first switch is greater than its turn-off threshold, when the first switch switches from the turn-on state to the turn-off state, the controller can control the gate voltage of the first switch to decrease until the gate voltage of the first switch is less than or equal to the turn-off threshold, at which point the first switch is completely turned off.

[0081] In some feasible implementations, such as Figure 3As shown, rapid turn-off of the first switch in the fifth stage does not cause EMI or voltage stress, while rapid turn-off of the first switch in the sixth stage directly causes EMI and voltage stress. Therefore, the controller can... Figure 3 At the start of the fifth stage, as shown, the gate voltage of the first switch decreases rapidly to accelerate its turn-off speed. Figure 3 At the start of the sixth stage, the controller can reduce the turn-off speed of the first switch in the sixth stage, thereby reducing the rate of decrease of the gate voltage of the first switch and avoiding large voltage stress and EMI.

[0082] Understandably, when the switching rate of the first switch is relatively slow (i.e., the turn-on and turn-off speeds are small), the controller can reduce voltage stress and EMI by controlling the gate voltage of the first switch to decrease at different rates in different stages. However, as the requirements for the switching rate of the first switch in power conversion equipment increase, the turn-off speed of the first switch is also becoming faster. When the turn-off speed of the first switch is very fast, the controller cannot effectively reduce voltage stress and EMI simply by controlling the rate of decrease of the gate voltage of the first switch in different stages.

[0083] For example, to meet the switching speed requirements of power conversion devices, the controller needs to quickly turn off the first switch. Therefore, when the turn-off moment of the first switch arrives, the controller provides a drive current to the first switch, causing the gate voltage of the first switch to drop rapidly. The arrival of the turn-off moment of the first switch can be understood as... Figure 3 The fifth stage is shown. Further, at the start of the sixth stage, to reduce voltage stress and EMI, the controller can reduce the drive current supplied to the first switch, thus slowing the rate of voltage drop at the first switch's gate voltage. However, because the gate voltage of the first switch drops too quickly in the fifth stage, although the controller slows down the rate of voltage drop in the sixth stage, the first switch still generates significant voltage stress and EMI.

[0084] Therefore, in the power conversion device provided in this application embodiment, after the controller arrives at the turn-off time of the first switch and provides a first drive current to the gate of the first switch to control the gate voltage of the first switch to drop, the controller can further obtain the voltage difference between the first electrode and the second electrode of the first switch through the first voltage detection terminal, and when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a first threshold, provide a second drive current to the gate of the first switch to control the gate voltage of the first switch to rise.

[0085] It should be noted that rapid turn-off of the first switch will not cause voltage stress or EMI if the voltage difference between the first and second electrodes of the first switch is greater than or equal to the first threshold. Figure 3 The fifth stage is shown. When the voltage difference between the first electrode and the second electrode of the first switching transistor is greater than or equal to the first threshold, it indicates that the first switching transistor has entered a stage where EMI and voltage stress may be generated significantly. Figure 3 The sixth and seventh stages are shown. At this time, in order to reduce the voltage stress and EMI generation of the first switching transistor, the controller can control the gate voltage of the first switching transistor to increase, so as to counteract the voltage stress caused by the rapid drop of the gate voltage of the first switching transistor under the action of the first drive current, thereby effectively reducing the voltage stress and EMI generation.

[0086] For example, when the first switch turns off, the controller provides a first drive current to the gate of the first switch to control the rapid drop in the gate voltage. Further, to minimize voltage stress and EMI that may be caused by the rapid drop in gate voltage, after the controller detects that the voltage difference between the first and second electrodes of the first switch is greater than or equal to a first threshold, the controller provides a second drive current to the gate of the first switch to increase the gate voltage. At this point, even if the gate voltage of the first switch drops too quickly under the drive of the first drive current, the controller's control of the gate voltage increase by the second drive current after the voltage difference between the first and second electrodes of the first switch is greater than or equal to the first threshold can offset the negative effects of the rapid drop in the gate voltage, thereby reducing voltage stress and EMI. Even if the controller only slows down the rate of decrease of the gate voltage, severe voltage stress and EMI may still occur.

[0087] In some feasible implementations, such as Figure 3As shown, in the seventh stage, the rapid turn-off of the first switch directly leads to EMI and voltage stress. However, in the subsequent eighth stage, the rapid turn-off of the first switch does not cause EMI or voltage stress. Therefore, in order to reduce voltage stress and EMI while accelerating the turn-off speed of the first switch to reduce its turn-off losses, the controller provides a second drive current to the gate of the first switch. After the gate voltage of the first switch increases, the controller can further obtain the voltage difference between the first and second electrodes of the first switch through the first voltage detection terminal. When the voltage difference between the first and second electrodes of the first switch is greater than or equal to a second threshold, a third drive current is provided to the gate of the first switch to control the gate voltage of the first switch to decrease rapidly until the gate voltage of the first switch is less than or equal to the aforementioned turn-off threshold, i.e., the first switch is turned off.

[0088] It should be noted that before the gate voltage of the first switching transistor rises to a level greater than or equal to the second threshold, the first switching transistor is in a stage where EMI and voltage stress may be generated significantly. Figure 3 The seventh stage is shown. When the voltage difference between the first and second electrodes of the first switching transistor is greater than or equal to the second threshold, the rapid turn-off of the first switching transistor will not cause voltage stress or EMI. Figure 3 The eighth stage is shown. In order to enable the first switch to be turned off quickly and reduce the turn-off loss of the first switch, the controller can control the gate voltage of the first switch to drop rapidly when the voltage difference between the first electrode and the second electrode of the first switch is detected by the first voltage detection terminal to be greater than or equal to the second threshold, until the gate voltage of the first switch is less than or equal to the turn-off threshold, that is, the first switch is turned off.

[0089] For example, when the controller detects through the first voltage detection terminal that the voltage difference between the first electrode and the second electrode is greater than or equal to a first threshold, it provides a second drive current to the gate of the first switch to control the gate voltage of the first switch to rise slowly, thereby reducing the voltage stress and EMI generated by the first switch. Furthermore, to accelerate the turn-off speed of the first switch and reduce its turn-off losses, when the controller detects through the first voltage detection terminal that the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a second threshold, the controller provides a third drive current to the gate of the first switch, causing the gate voltage of the first switch to change from rising to rapidly falling, thereby reducing the turn-off losses of the first switch.

[0090] In some feasible implementations, the controller may also provide a second drive current to the gate of the first switch to control the gate voltage of the first switch to rise, while simultaneously obtaining the duration for which the gate of the first switch provides the second drive current, and when the duration for which the second drive current is provided is greater than or equal to a time threshold, provide a third drive current to the gate of the first switch to control the gate voltage of the first switch to drop rapidly until the gate voltage of the first switch is less than or equal to the aforementioned turn-off threshold, i.e., the first switch is turned off.

[0091] It is understandable that before the controller provides the second drive current to the gate of the first switch for a period of time less than the aforementioned time threshold, the first switch is in a phase where EMI and voltage stress may be generated significantly, such as... Figure 3 The seventh stage is shown. When the duration for which the controller provides the second drive current to the gate of the first switch is greater than or equal to the time threshold, the rapid turn-off of the first switch will not cause voltage stress or EMI. Figure 3 The eighth stage is shown. In order to enable the first switch to turn off quickly and reduce the turn-off loss of the first switch, the controller can provide a third drive current to the gate of the first switch when the duration of providing the second drive current to the gate of the first switch is greater than or equal to the aforementioned time threshold. This causes the gate voltage of the first switch to change from rising to falling rapidly, thereby reducing the turn-off loss of the first switch, until the gate voltage of the first switch is less than or equal to the turn-off threshold, that is, the first switch is turned off.

[0092] To facilitate understanding of the process by which a power conversion device controls the first switching transistor to turn off via a controller, the following content combines... Figure 5 To illustrate, Figure 5 This is a waveform diagram of the first switching transistor provided in an embodiment of this application. Figure 5 The PWM signal shown is the signal that controls the first switch to turn off. Vg is the gate voltage of the first switch, Ig is the drive current provided by the controller to the gate of the first switch (such as the first drive current, the second drive current or the third drive current mentioned above), and Vq is the voltage difference between the first electrode and the second electrode of the first switch.

[0093] It is understandable that, such as Figure 5When time T0 arrives, the controller receives a low-level PWM signal for controlling the first switching transistor, indicating the turn-off time of the first switching transistor. At this time, the first switching transistor switches from the on state to the off state, and the controller can provide a first drive current Isk0 to the gate of the first switching transistor through the current control terminal to control the gate voltage Vg of the first switching transistor to decrease from its maximum value Vsk0. The first drive current Isk0 is a pull-down current relative to the gate of the first switching transistor, meaning that the first drive current Isk0 can pull down the gate voltage of the first switching transistor. If combined with... Figure 4 As shown, the direction of the first driving current Isk0 is... Figure 4 The driving current Ig flows in the opposite direction. Furthermore, as the first switch begins to turn off, the voltage difference Vq between the first and second electrodes of the first switch increases from zero.

[0094] At time T1, the controller detects that the voltage difference Vq between the first and second electrodes of the first switching transistor has increased to a first threshold Vst, indicating that the first switching transistor has entered a stage where EMI and voltage stress may be significantly generated. To reduce voltage stress and EMI, the controller provides a second drive current Isp to the gate of the first switching transistor through the current control terminal, thereby controlling the gate voltage Vg of the first switching transistor to rise from Vsk1. The second drive current Isp is a pull-up current relative to the gate of the first switching transistor, meaning that the second drive current Isp can pull up the gate voltage of the first switching transistor. (This is combined with...) Figure 4 As shown, the direction of the second driving current Isp is... Figure 4 The direction of the drive current Ig is consistent. In addition, although the gate voltage of the first switch starts to rise, it does not rise to a level greater than or equal to the turn-on threshold. Therefore, the first switch is still in a partially turned-off state, and the voltage difference Vq between the first electrode and the second electrode of the first switch will continue to increase.

[0095] It should be noted that although the voltage difference Vq between the first electrode and the second electrode of the first switching transistor will continue to increase, the controller provides a second drive current Isp to the gate of the first switching transistor, which raises the gate voltage of the first switching transistor. This prevents the voltage difference Vq from suddenly increasing during the turn-off process of the first switching transistor, thereby reducing the voltage stress and EMI generation of the first switching transistor.

[0096] At time T2, the controller detects that the voltage difference Vq between the first and second electrodes of the first switching transistor has increased to the second threshold Ven, or it can be characterized by the controller providing the second drive current to the gate of the first switching transistor for a duration greater than or equal to the time threshold. At this point, the first switching transistor enters a stage where even rapid turn-off will not cause significant EMI or voltage stress. To accelerate the turn-off speed of the first switching transistor and reduce its turn-off losses, the controller provides a third drive current Isk3 to the gate of the first switching transistor through the current control terminal, controlling the gate voltage Vg of the first switching transistor to decrease from Vsk3. The third drive current Isk3 is a pull-down current relative to the gate of the first switching transistor, meaning that the third drive current Isk3 can pull down the gate voltage of the first switching transistor. If combined with... Figure 4 As shown, the direction of the third driving current Isk3 is... Figure 4 The driving current Ig flows in the opposite direction. Furthermore, the voltage difference Vq between the first and second electrodes of the first switch continues to increase.

[0097] Understandably, under the pull-down effect of the third drive current Isk3, the gate voltage of the first switch rapidly decreases until it drops to the turn-off threshold Vsk4, at which point the first switch is completely turned off. At this time, the voltage difference Vq between the first and second electrodes of the first switch is equal to the operating voltage Vbus of the bus.

[0098] It should be noted that the specific methods for determining the first drive current, second drive current, and third drive current, as well as the first threshold, second threshold, and time threshold, are not detailed here. Furthermore, the turn-off process of the second switch connected in series with the first switch in the power changing device can refer to the specific implementation method of the first switch described above, and will not be elaborated upon in this application embodiment.

[0099] In this embodiment, when the turn-off time of the first switch arrives, the power conversion device controls the gate voltage of the first switch to decrease through the controller, and controls the gate voltage of the first switch to increase when the voltage difference across the first switch reaches a first threshold, which can effectively reduce voltage stress and EMI generation. Furthermore, when the voltage difference across the first switch reaches a second threshold, or when the duration of the controller providing the second drive current (i.e., the duration of the gate voltage increase of the first switch) reaches a time threshold, the power conversion device controls the gate voltage of the first switch to change from increasing to decreasing through the controller until the first switch is completely turned off. This can reduce voltage stress and EMI generation while improving the turn-off speed of the first switch, thereby reducing turn-off losses.

[0100] In some feasible implementations, as can be seen from the above, the first switching transistor has different operating characteristics at different stages of the turn-off process. For example... Figure 3 As shown, in the sixth stage, the first switch enters the Miller plateau stage, at which point the first switch begins to turn off, and the voltage Vq across it increases accordingly. The drive current Ig provided by the controller to the first switch affects the rate of change of the voltage Vq across it. Specifically, the larger the drive current Ig provided by the controller, the faster the rate of change of the voltage Vq across the first switch, and the faster the turn-off speed of the first switch. In the seventh stage, the first switch enters the current-off stage, and the current Ic of the first switch begins to decrease. As the current Ic decreases, the voltage Vq across the first switch also decreases. At this time, the drive current Ig provided by the controller to the first switch has a more significant impact on the current Ic.

[0101] Therefore, although the first switching transistor may generate voltage stress and EMI during rapid turn-off in both the Miller plateau stage and the current turn-off stage, the voltage stress and EMI caused by rapid turn-off are smaller when the first switching transistor enters the Miller plateau stage compared to the current turn-off stage. To accelerate the turn-off speed of the first switching transistor and reduce turn-off losses, the controller can control the gate voltage of the first switching transistor to decrease slowly when it enters the Miller plateau stage, thereby accelerating the turn-off of the first switching transistor while reducing voltage stress and EMI generation. Furthermore, the controller can control the gate voltage of the first switching transistor to increase when it enters the current turn-off stage, thereby minimizing voltage stress and EMI generation.

[0102] In some feasible implementations, the power conversion device provided in this application can determine the timing of the first switching transistor entering the Miller plateau stage and the current-off stage through a controller. Specifically, the controller in the power conversion device can be connected to the gate of the first switching transistor through a second voltage detection terminal to detect the gate voltage of the first switching transistor.

[0103] In some feasible implementations, the controller can also obtain the gate voltage of the first switch transistor through an external detection device. This detection device can be connected to the gate of the first switch transistor and send the detected gate voltage to the controller. It should be noted that the above is merely an example, and the specific implementation of the controller obtaining the gate voltage of the first switch transistor in this application does not limit the specific method. Further, when the controller detects through the second voltage detection terminal that the gate voltage of the first switch transistor is less than or equal to a third threshold, indicating that the first switch transistor has entered the aforementioned Miller plateau stage, the controller can control the rate of decrease of the gate voltage of the first switch transistor to decrease. Here, the controller can control the rate of decrease of the gate voltage of the first switch transistor to decrease means that the rate of decrease of the gate voltage of the first switch transistor is less than a first rate of decrease, where the first rate of decrease is the rate of decrease of the gate voltage of the first switch transistor under the action of the first driving current.

[0104] It should be noted that before the gate voltage of the first switching transistor is less than or equal to the third threshold, the first switching transistor is in a stage where rapid turn-off will not lead to voltage stress or EMI. Figure 3 The fifth stage is shown. At this point, the gate voltage of the first switch can drop rapidly. Furthermore, when the gate voltage of the first switch is less than or equal to the third threshold, it indicates that the first switch has entered a stage where EMI and voltage stress may occur significantly, such as... Figure 3 The sixth stage is shown. At this point, in order to reduce the voltage stress and EMI generation of the first switching transistor without significantly affecting its turn-off speed, the controller can reduce the rate of decrease of the gate voltage of the first switching transistor, thereby effectively reducing voltage stress and EMI generation.

[0105] For example, when the first switch turns off, the controller provides a first drive current to the gate of the first switch to control the gate voltage of the first switch to drop rapidly. Further, to reduce voltage stress and EMI that may be caused by the rapid drop in gate voltage, when the controller detects through the second voltage detection terminal that the gate voltage of the first switch is less than or equal to a third threshold, the controller provides a fourth drive current to the gate of the first switch to reduce the rate of decrease of the gate voltage. That is, the rate of decrease of the gate voltage of the first switch under the fourth drive current is smaller than the rate of decrease under the first drive current (i.e., the first rate of decrease). At this time, because the controller controls the rate of decrease of the gate voltage of the first switch to decrease, voltage stress and EMI generation can be reduced without affecting the turn-off speed of the first switch.

[0106] To facilitate understanding of the process by which a power conversion device controls the first switching transistor to turn off via a controller, the following content combines... Figure 6To illustrate, Figure 6 Another waveform diagram of the first switching transistor provided in an embodiment of this application. Wherein, Figure 6 The PWM signal shown is the signal that controls the first switch to turn off. Vg is the gate voltage of the first switch, Ig is the drive current provided by the controller to the gate of the first switch (such as the first drive current, second drive current, third drive current or fourth drive current mentioned above), and Vq is the voltage difference between the first electrode and the second electrode of the first switch.

[0107] It is understandable that, such as Figure 6 When time T0 arrives, the controller receives a low-level PWM signal for controlling the first switching transistor, indicating the turn-off time of the first switching transistor. At this time, the first switching transistor switches from the on state to the off state, and the controller can provide a first drive current Isk0 to the gate of the first switching transistor through the current control terminal to control the gate voltage Vg of the first switching transistor to decrease from its maximum value Vsk0. The first drive current Isk0 is a pull-down current relative to the gate of the first switching transistor, meaning that the first drive current Isk0 can pull down the gate voltage of the first switching transistor. If combined with... Figure 4 As shown, the direction of the first driving current Isk0 is... Figure 4 The driving current Ig flows in the opposite direction. Furthermore, as the first switch begins to turn off, the voltage difference Vq between the first and second electrodes of the first switch increases from zero.

[0108] At time T1, the controller detects that the gate voltage of the first switch has dropped to the third threshold Vsk1 via the second voltage detection terminal, indicating that the first switch has entered a stage where EMI and voltage stress may occur. To reduce voltage stress and EMI without significantly affecting the turn-off speed of the first switch, the controller provides a fourth drive current Isk2 to the gate of the first switch via the current control terminal, controlling the gate voltage Vg of the first switch to slowly decrease from Vsk1. The fourth drive current Isk2 is a pull-down current relative to the gate of the first switch, meaning it pulls down the gate voltage of the first switch. (This is combined with...) Figure 4 As shown, the direction of the fourth driving current Isk2 is... Figure 4 The driving current Ig flows in the opposite direction. Furthermore, the fourth driving current Isk2 can be smaller than the first driving current Isk1, which allows the rate of decrease of the gate voltage Vg of the first switch after time T1 to be less than before time T1. Simultaneously, the voltage difference Vq between the first and second electrodes of the first switch will continue to increase.

[0109] At time T2, the controller detects that the voltage difference Vq between the first and second electrodes of the first switching transistor has increased to a first threshold Vst, indicating that the first switching transistor has entered a stage where EMI and voltage stress may be generated significantly. To reduce voltage stress and EMI, the controller provides a second drive current Isp to the gate of the first switching transistor through the current control terminal, thereby controlling the gate voltage Vg of the first switching transistor to rise from Vsk2. The second drive current Isp acts as a pull-up current relative to the gate of the first switching transistor. Furthermore, although the gate voltage of the first switching transistor begins to rise, it does not rise above or exceed the conduction threshold. Therefore, the first switching transistor remains in an incompletely off state, and the voltage difference Vq between the first and second electrodes of the first switching transistor will continue to increase.

[0110] It should be noted that although the voltage difference Vq between the first electrode and the second electrode of the first switching transistor will continue to increase, the controller provides a second drive current Isp to the gate of the first switching transistor, which raises the gate voltage of the first switching transistor. This prevents the voltage difference Vq from suddenly increasing during the turn-off process of the first switching transistor, thereby reducing the voltage stress and EMI generation of the first switching transistor.

[0111] At time T3, the controller detects that the voltage difference Vq between the first and second electrodes of the first switching transistor has increased to the second threshold Ven, indicating that the first switching transistor has entered a stage where even rapid turn-off will not cause significant EMI or voltage stress. To accelerate the turn-off speed of the first switching transistor and reduce its turn-off losses, the controller provides a third drive current Isk3 to the gate of the first switching transistor through the current control terminal, controlling the gate voltage Vg of the first switching transistor to decrease from Vsk3. The third drive current Isk3 is a pull-down current relative to the gate of the first switching transistor. The voltage difference Vq between the first and second electrodes of the first switching transistor continues to increase.

[0112] Understandably, under the pull-down effect of the third drive current Isk3, the gate voltage of the first switch drops rapidly. At time T4, the gate voltage of the first switch drops to the turn-off threshold Vsk4, indicating that the first switch is completely turned off. At this time, the voltage difference Vq between the first and second electrodes of the first switch is equal to the operating voltage Vbus of the bus.

[0113] It should be noted that the turn-off process of the second switch connected in series with the first switch in the power changing device can refer to the specific implementation method of the first switch described above, and will not be repeated here in the embodiments of this application.

[0114] In some feasible implementations, in the power conversion device provided in the embodiments of this application, the controller can determine the magnitude of the first drive current based on the magnitude of the drive current provided to the gate of the first switch when controlling the first switch to turn off at a target turn-off speed.

[0115] As described above, when the first switch turns off, it indicates that the first switch has entered a stage where it can be quickly turned off without causing EMI or voltage stress. At this time, the controller can provide a first drive current to the first switch, causing its gate voltage to drop rapidly. Therefore, the function of this first drive current is to quickly drive the gate voltage of the first switch down. To determine the magnitude of this first drive current, the controller can use multiple candidate drive currents as the gate drive current of the first switch to drive it through multiple turn-off tests. Furthermore, the controller can use one of the candidate drive currents used when the first switch reaches the target turn-off speed during these multiple turn-off tests as the first drive current.

[0116] It should be noted that the aforementioned target turn-off speed refers to the minimum turn-off speed of the first switching transistor to meet the switching rate requirements of the power conversion device. In other words, when the turn-off speed of the first switching transistor is greater than or equal to this target turn-off speed, the switching rate requirements of the power conversion device can be met without damaging the first switching transistor. Conversely, when the turn-off speed of the first switching transistor is less than the target turn-off speed, the switching rate requirements of the power conversion device are not met.

[0117] For example, suppose the controller uses Isk10, Isk11, and Isk12 as the aforementioned candidate drive currents. Further, when the controller provides candidate drive current Isk10 to the gate of the first switch to drive it to turn off, the turn-off speed of the first switch is obtained as v0. When the controller provides candidate drive current Isk11 to the gate of the first switch to drive it to turn off, the turn-off speed of the first switch is obtained as v1. When the controller provides candidate drive current Isk12 to the gate of the first switch to drive it to turn off, the turn-off speed of the first switch is obtained as v2. Now, suppose the target turn-off speed of the first switch is va, and v0 < v1 < va < v2. Therefore, when the controller provides candidate drive current Isk12 to the gate of the first switch to drive it to turn off, the turn-off speed of the first switch is greater than the turn-off speed when using other candidate drive currents, and is greater than or equal to the target turn-off speed va. At the same time, when the controller drives the first switch to turn off with the candidate drive current, it will not damage the first switch. Therefore, the controller can use the candidate drive current Isk12 as the first drive current of the first switch.

[0118] In some feasible implementations, in the power conversion device provided in the embodiments of this application, the controller can determine the magnitude of the third drive current based on the magnitude of the drive current provided to the gate of the first switch when controlling the first switch to turn off at a target turn-off speed.

[0119] It should be noted that the specific implementation of the controller determining the magnitude of the third drive current can refer to the specific implementation of determining the magnitude of the first drive current described above, and will not be repeated in this application embodiment. Furthermore, the magnitudes of the first drive current and the third drive current can be the same or different, and this application embodiment does not limit this.

[0120] In some feasible implementations, the controller may determine the magnitude of the second drive current based on the following:

[0121] It should be noted that the magnitude of the voltage stress generated by the first switching transistor is related to the rate of change of the voltage difference between its first and second electrodes, which in turn is related to the load connected to the power conversion device. Specifically, when the load is heavy, meaning the required supply current is large, the voltage difference between the first and second electrodes of the first switching transistor changes more rapidly to provide sufficient current, resulting in greater voltage stress generated by the first switching transistor. Conversely, when the load is light, meaning the required supply current is small, the voltage difference between the first and second electrodes changes more slowly, resulting in less voltage stress generated by the first switching transistor.

[0122] It is understandable that the rate of change of the voltage difference between the first and second electrodes of the first switching transistor can be characterized by the rate of change of the voltage difference between the first and second electrodes of the first switching transistor. Specifically, this rate of change of the voltage difference between the first and second electrodes of the first switching transistor refers to the magnitude of the change in the voltage difference between the first and second electrodes of the first switching transistor within a certain time range.

[0123] The greater the rate of change of the voltage difference between the first and second electrodes of the first switching transistor, the faster the voltage difference changes between them; that is, the faster the voltage difference rises. Therefore, the voltage stress generated by the first switching transistor will be greater. Conversely, the smaller the rate of change of the voltage difference between the first and second electrodes, the slower the voltage difference changes; that is, the slower the voltage difference rises. Therefore, the voltage stress generated by the first switching transistor will be smaller.

[0124] Therefore, in this embodiment, the controller can determine the magnitude of the second drive current based on the rate of change of the voltage difference between the first electrode and the second electrode of the first switch. Furthermore, when the voltage stress generated by the first switch is relatively large, indicating a heavy load connected to the power conversion device, the controller can increase the output second drive current to make the gate voltage of the first switch rise faster, thereby effectively reducing the voltage stress generated by the first switch. When the voltage stress generated by the first switch is relatively small, indicating a light load connected to the power conversion device, the controller can decrease the output second drive current to make the gate voltage of the first switch rise more slowly, thereby appropriately increasing the turn-off speed of the first switch while reducing the voltage stress generated by the first switch.

[0125] In some feasible implementations, the controller can detect the first electrode voltage of the first switch through the first voltage detection terminal after the first switch is turned off and after the controller provides the first drive current to the gate of the first switch, so as to obtain the rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

[0126] For example, such as Figure 5 As shown, after time T0 arrives, the controller provides a first drive current Isk1 to the gate of the first switching transistor. Simultaneously, the controller detects the voltage of the first electrode of the first switching transistor through the first voltage detection terminal to obtain the voltage difference between the first and second electrodes of the first switching transistor. Further, assuming the controller obtains a voltage difference of Vh1 between the first and second electrodes of the first switching transistor, and after a preset time range, obtains a voltage difference of Vh2 between the first and second electrodes of the first switching transistor, the controller can obtain the rate of change of the voltage difference between the first and second electrodes of the first switching transistor within this preset time range: dv / dt = (Vh2 - Vh1) / T, where T is the aforementioned preset time range.

[0127] In some feasible implementations, after the controller provides the aforementioned fourth drive current to the gate of the first switch, it can detect the first electrode voltage of the first switch through the first voltage detection terminal to obtain the rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

[0128] For example, such as Figure 6 As shown, after time T1 arrives, the controller provides a fourth drive current Isk2 to the gate of the first switching transistor. Simultaneously, the controller detects the voltage of the first electrode of the first switching transistor through the first voltage detection terminal to obtain the voltage difference between the first and second electrodes of the first switching transistor. Further, assuming the controller obtains a voltage difference of Vh1 between the first and second electrodes of the first switching transistor, and after a preset time range, obtains a voltage difference of Vh2 between the first and second electrodes of the first switching transistor, the controller can obtain the rate of change of the voltage difference between the first and second electrodes of the first switching transistor within this preset time range: dv / dt = (Vh2 - Vh1) / T, where T is the aforementioned preset time range.

[0129] It is understood that the controller can also obtain the rate of change of voltage difference between the first electrode and the second electrode of the first switch in other ways, which will not be illustrated in the embodiments of this application.

[0130] In some feasible implementations, after obtaining the rate of change of the voltage difference between the first and second electrodes of the first switching transistor, the controller can determine a drive current value corresponding to the rate of change of the voltage difference as the magnitude of the second drive current based on a preset relationship table. The preset relationship table includes drive current values ​​corresponding one-to-one with different rates of change of voltage difference. This preset relationship table can be obtained based on multiple turn-off tests of the first switching transistor or practical experience; this application does not limit this approach.

[0131] In the power conversion device provided in this application embodiment, the controller can increase the magnitude of the second drive current when the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor is relatively large, thereby effectively reducing the voltage stress generated by the first switching transistor. Conversely, the controller can decrease the magnitude of the second drive current when the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor is relatively small, thereby reducing the voltage stress generated by the first switching transistor while appropriately increasing the turn-off speed of the first switching transistor.

[0132] For example, when the controller obtains that the rate of change of the voltage difference between the first electrode and the second electrode of the first switch is equal to a1, the controller can determine the magnitude of the second drive current as Isp1 based on the rate of change of the voltage difference a1. When the controller obtains that the rate of change of the voltage difference between the first electrode and the second electrode of the first switch is equal to a2, and a2 > a1, the controller can determine the magnitude of the second drive current as Isp2 based on the rate of change of the voltage difference a2, and Isp2 > Isp1.

[0133] In some feasible implementations, the controller can determine the magnitude of the second drive current based not only on the rate of change of the voltage difference between the first electrode and the second electrode of the first switch, but also on the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference.

[0134] It should be noted that, as can be seen from the above, the magnitude of the voltage stress generated by the first switching transistor is related to the rate of change of the voltage difference between the first and second electrodes of the first switching transistor. The magnitude of the change of the voltage difference between the first and second electrodes of the first switching transistor can also be characterized by the time it takes for the voltage difference between the first and second electrodes of the first switching transistor to increase from the first voltage difference to the second voltage difference.

[0135] Specifically, the longer the time it takes for the voltage difference between the first and second electrodes of the first switching transistor to increase from the first voltage difference to the second voltage difference, the slower the change in voltage difference between the first and second electrodes of the first switching transistor, and thus the lower the voltage stress generated by the first switching transistor. Conversely, the shorter the time it takes for the voltage difference between the first and second electrodes of the first switching transistor to increase from the first voltage difference to the second voltage difference, the faster the change in voltage difference between the first and second electrodes of the first switching transistor, and thus the greater the voltage stress generated by the first switching transistor.

[0136] Therefore, in this embodiment, the controller can determine the magnitude of the second drive current based on the time it takes for the voltage difference between the first electrode and the second electrode of the first switch to increase from the first voltage difference to the second voltage difference. Furthermore, when the voltage stress generated by the first switch is relatively large, indicating a heavy load connected to the power conversion device, the controller can increase the output second drive current to make the gate voltage of the first switch rise faster, thereby effectively reducing the voltage stress generated by the first switch. When the voltage stress generated by the first switch is relatively small, indicating a light load connected to the power conversion device, the controller can decrease the output second drive current to make the gate voltage of the first switch rise more slowly, thereby appropriately increasing the turn-off speed of the first switch while reducing the voltage stress generated by the first switch.

[0137] In some feasible implementations, the controller can detect the first electrode voltage of the first switch through the first voltage detection terminal after the first switch is turned off and after the controller provides the first drive current to the gate of the first switch, so as to obtain the time length of time for the voltage difference between the first electrode and the second electrode of the first switch to increase from the first voltage difference to the second voltage difference.

[0138] For example, such as Figure 5 As shown, after time T0 arrives, the controller provides a first drive current Isk1 to the gate of the first switch transistor. Simultaneously, the controller detects the voltage at the first electrode of the first switch transistor via a first voltage detection terminal to obtain the voltage difference between the first and second electrodes of the first switch transistor. Furthermore, the controller can obtain the time length T taken for the voltage difference between the first and second electrodes of the first switch transistor to rise from Vh1 to Vh2.

[0139] In some feasible implementations, after the controller provides the aforementioned fourth drive current to the gate of the first switch, it can detect the first electrode voltage of the first switch through the first voltage detection terminal to obtain the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference.

[0140] For example, such as Figure 6As shown, after time T1 arrives, the controller provides a fourth drive current Isk2 to the gate of the first switch. Simultaneously, the controller detects the voltage at the first electrode of the first switch via the first voltage detection terminal to obtain the voltage difference between the first and second electrodes of the first switch. Furthermore, the controller can obtain the time length T taken for the voltage difference between the first and second electrodes of the first switch to rise from Vh1 to Vh2.

[0141] It is understood that the controller can also obtain the time length of time for the voltage difference between the first electrode and the second electrode of the first switch to increase from the first voltage difference to the second voltage difference through other means. Examples of these embodiments will not be given here.

[0142] It should be noted that the controller can pre-set specific values ​​for the first voltage difference and the second voltage difference. In practical applications, these values ​​can be calculated based on the bus operating voltage and the target turn-off time of the first switching transistor. Specifically, the controller needs to acquire the aforementioned time length T before the first switching transistor is completely turned off, i.e., before the voltage across the first switching transistor reaches the bus operating voltage. In this case, the first and second voltage differences will be less than the bus operating voltage of 5V. Furthermore, since the controller can acquire the aforementioned time length T as early as possible during the turn-off process of the first switching transistor to adjust its gate voltage in a timely manner, the pre-set first and second voltage differences in the controller are typically positively correlated with the target turn-off time of the first switching transistor.

[0143] For example, assuming the bus operating voltage is 5V and the target turn-off time of the first switch is 100ms, the controller needs to obtain the aforementioned time length T within the first 40ms of the first switch's turn-off process. The controller can pre-set the second voltage difference to 5V × (40ms / 100ms) = 2V, and the first voltage difference can be 1V. It is understood that after the turn-off time of the first switch arrives, the controller can detect the voltage difference between the first and second electrodes of the first switch and obtain the time it takes for the voltage difference between the first and second electrodes to increase from 1V to 2V, which is the aforementioned time length T. The above is merely an example and does not constitute a limitation on the embodiments of this application.

[0144] In some feasible implementations, after the controller obtains the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference, it can determine a drive current value corresponding to that time length as the magnitude of the second drive current based on a preset relationship table. The preset relationship table includes drive current values ​​corresponding one-to-one with different time lengths. This preset relationship table can be obtained based on multiple turn-off tests of the first switch or practical experience; this application does not limit this approach.

[0145] In the power conversion device provided in this application embodiment, the controller can increase the magnitude of the second drive current when the time duration for the voltage difference between the first electrode and the second electrode of the first switching transistor to increase from the first voltage difference to the second voltage difference is relatively small, thereby effectively reducing the voltage stress generated by the first switching transistor. Conversely, the controller can decrease the magnitude of the second drive current when the time duration for the voltage difference between the first electrode and the second electrode of the first switching transistor to increase from the first voltage difference to the second voltage difference is relatively large, thereby reducing the voltage stress generated by the first switching transistor while appropriately increasing the turn-off speed of the first switching transistor.

[0146] For example, when the controller obtains that the time length for the voltage difference between the first electrode and the second electrode of the first switch to increase from the first voltage difference to the second voltage difference is equal to t1, the controller can determine the magnitude of the second drive current as Isp1 based on this time length t1. When the controller obtains that the time length for the voltage difference between the first electrode and the second electrode of the first switch to increase from the first voltage difference to the second voltage difference is equal to t2, and t2 > t1, the controller can determine the magnitude of the second drive current as Isp2 based on this time length t2, and Isp2 < Isp1.

[0147] In some feasible implementations, when the controller detects that the voltage difference between the first electrode and the second electrode of the first switching transistor is greater than or equal to a first threshold at the first voltage detection terminal, it can first provide a second driving current to the gate of the first switching transistor. The value of the second driving current can be preset. Furthermore, while providing the second driving current to the gate of the first switching transistor, the controller can obtain the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor, and adjust the magnitude of the second driving current based on the rate of change of the voltage difference.

[0148] Specifically, when the controller provides a second drive current to the gate of the first switching transistor, it can detect the voltage of the first electrode of the first switching transistor through the first voltage detection terminal to obtain the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor. The specific implementation method for the controller to obtain the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor can be found above, and will not be repeated here.

[0149] In some feasible implementations, further, after obtaining the rate of change of the voltage difference between the first electrode and the second electrode of the first switch, the controller can adjust the second drive current supplied to the gate of the first switch by decreasing the rate of change of the voltage difference based on the magnitude of the rate of change of the voltage difference until the rate of change of the voltage difference between the first electrode and the second electrode of the first switch reaches a target value, thus completing the adjustment of the second drive current. The target value of the rate of change of the voltage difference between the first electrode and the second electrode of the first switch can be adjusted according to the needs of the actual application scenario, and this application embodiment does not limit this.

[0150] In some feasible implementations, after obtaining the rate of change of the voltage difference between the first and second electrodes of the first switching transistor, the controller can also determine a drive current value corresponding to the rate of change of the voltage difference as the target value for adjusting the second drive current based on a preset relationship table. The preset relationship table includes drive current values ​​that correspond one-to-one with different rates of change of voltage difference. This preset relationship table can be obtained based on multiple turn-off tests of the first switching transistor or practical experience; this application does not limit this approach.

[0151] It is understandable that after determining the target value for adjusting the second drive current, the controller can adjust the second drive current supplied to the gate of the first switch so that the value of the second drive current can be equal to the target value, thereby completing the adjustment of the second drive current.

[0152] In some feasible implementations, when the controller detects that the voltage difference between the first electrode and the second electrode of the first switching transistor is greater than or equal to a first threshold at the first voltage detection terminal, it can first provide a second driving current to the gate of the first switching transistor. The value of the second driving current can be preset. Furthermore, while providing the second driving current to the gate of the first switching transistor, the controller can obtain the time length during which the voltage difference between the first electrode and the second electrode of the first switching transistor increases from the first voltage difference to the second voltage difference, and adjust the magnitude of the second driving current based on the time length.

[0153] Specifically, when the controller provides a second drive current to the gate of the first switching transistor, it can detect the voltage of the first electrode of the first switching transistor through the first voltage detection terminal to obtain the time length during which the voltage difference between the first electrode and the second electrode of the first switching transistor increases from the first voltage difference to the second voltage difference. The specific implementation method for the controller to obtain the time length during which the voltage difference between the first electrode and the second electrode of the first switching transistor increases from the first voltage difference to the second voltage difference can be found above, and will not be repeated here.

[0154] In some feasible implementations, further, after the controller obtains the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference, it can adjust the second drive current supplied to the gate of the first switch by decreasing based on the magnitude of this time length until the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference reaches a target value, thus completing the adjustment of the second drive current. The target value of the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference can be adjusted according to the needs of the actual application scenario, and this application embodiment does not limit this.

[0155] In some feasible implementations, after the controller obtains the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference, it can also determine a drive current value corresponding to that time length as the target value for adjusting the second drive current based on a preset relationship table. The preset relationship table includes drive current values ​​that correspond one-to-one with different time lengths. This preset relationship table can be obtained based on multiple turn-off tests of the first switch or practical experience; this application does not limit this approach.

[0156] It is understandable that after determining the target value for adjusting the second drive current, the controller can adjust the second drive current supplied to the gate of the first switch so that the value of the second drive current can be equal to the target value, thereby completing the adjustment of the second drive current.

[0157] In some feasible implementations, the controller may determine the magnitude of the aforementioned time threshold based on the following:

[0158] It should be noted that the duration for which the controller provides the second drive current to the gate of the first switching transistor is related to the magnitude of the voltage stress generated by the first switching transistor. The longer the duration for which the controller provides the second drive current to the gate of the first switching transistor, i.e., the larger the aforementioned time threshold, the more the voltage stress generated by the first switching transistor can be reduced. Therefore, the controller can determine the magnitude of the aforementioned time threshold based on the potential voltage stress generated by the first switching transistor.

[0159] As can be seen from the above, the magnitude of the voltage stress generated by the first switching transistor is related to the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor, and the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor can be characterized by the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor.

[0160] Understandably, the greater the rate of change of the voltage difference between the first and second electrodes of the first switching transistor, the faster the voltage difference changes between them, meaning the voltage stress generated by the first switching transistor will be greater. Consequently, the controller needs to provide the second drive current to the gate of the first switching transistor for a longer period of time, i.e., the aforementioned time threshold will be larger. Conversely, the smaller the rate of change of the voltage difference between the first and second electrodes of the first switching transistor, the slower the voltage difference changes between them, meaning the voltage stress generated by the first switching transistor will be smaller. Consequently, the controller needs to provide the second drive current to the gate of the first switching transistor for a shorter period of time, i.e., the aforementioned time threshold will be smaller.

[0161] Furthermore, when the rate of change of the voltage difference between the first and second electrodes of the first switch is relatively large, the controller can increase the aforementioned time threshold to increase the duration of outputting the second drive current to the gate of the first switch, thereby effectively reducing the voltage stress generated by the first switch. When the rate of change of the voltage difference between the first and second electrodes of the first switch is relatively small, the controller can decrease the aforementioned time threshold to shorten the duration of outputting the second drive current to the gate of the first switch, thereby appropriately increasing the turn-off speed of the first switch while reducing the voltage stress generated by the first switch.

[0162] It should be noted that the specific implementation method for the controller to obtain the rate of change of voltage difference between the first electrode and the second electrode of the first switching transistor can be found in the above content, and will not be repeated here in the embodiments of this application.

[0163] In some feasible implementations, after obtaining the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor, the controller can determine a time length value corresponding to the rate of change of the voltage difference as the magnitude of the aforementioned time threshold based on a preset relationship table. The preset relationship table includes time length values ​​corresponding one-to-one with different values ​​of the rate of change of the voltage difference. This preset relationship table can be obtained based on multiple turn-off tests of the first switching transistor or practical experience; this application embodiment does not limit this.

[0164] In some feasible implementations, the controller can determine the magnitude of the time threshold not only based on the rate of change of the voltage difference between the first electrode and the second electrode of the first switch, but also based on the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference.

[0165] It should be noted that, as can be seen from the above, the magnitude of the voltage stress generated by the first switching transistor is related to the rate of change of the voltage difference between the first and second electrodes of the first switching transistor. The magnitude of the change of the voltage difference between the first and second electrodes of the first switching transistor can also be characterized by the time it takes for the voltage difference between the first and second electrodes of the first switching transistor to increase from the first voltage difference to the second voltage difference.

[0166] Specifically, the longer the time it takes for the voltage difference between the first and second electrodes of the first switching transistor to increase from the first voltage difference to the second voltage difference, the smaller the voltage stress generated by the first switching transistor. Therefore, the shorter the time required for the controller to provide the second drive current to the gate of the first switching transistor, i.e., the smaller the aforementioned time threshold. Conversely, the shorter the time it takes for the voltage difference between the first and second electrodes of the first switching transistor to increase from the first voltage difference to the second voltage difference, the greater the voltage stress generated by the first switching transistor. Therefore, the longer the time required for the controller to provide the second drive current to the gate of the first switching transistor, i.e., the larger the aforementioned time threshold.

[0167] Furthermore, when the time it takes for the voltage difference between the first and second electrodes of the first switch to increase from the first voltage difference to the second voltage difference is relatively short, the controller can increase the aforementioned time threshold to extend the time for outputting the second drive current to the gate of the first switch, thereby effectively reducing the voltage stress generated by the first switch. When the aforementioned time is relatively long, the controller can decrease the time threshold to shorten the time for outputting the second drive current to the gate of the first switch, thereby appropriately increasing the turn-off speed of the first switch while reducing the voltage stress generated by the first switch.

[0168] It should be noted that the specific implementation of the controller obtaining the time length of time for the voltage difference between the first electrode and the second electrode of the first switching transistor to increase from the first voltage difference to the second voltage difference can be found in the above content, and will not be repeated here in the embodiments of this application.

[0169] In some feasible implementations, after the controller obtains the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference, it can determine a threshold value corresponding to this time length as the magnitude of the aforementioned time threshold based on a preset relationship table. The preset relationship table includes threshold values ​​corresponding one-to-one with different time lengths. This preset relationship table can be obtained based on multiple turn-off tests of the first switch or practical experience; this application does not limit this approach.

[0170] In some feasible implementations, the following describes the principle of the controller controlling the first switch to turn on.

[0171] As can be seen from the above, the first switching transistor has different operating characteristics at different stages of the conduction process. Therefore, in order to reduce the conduction loss of the first switching transistor while reducing current stress and EMI, the power conversion device provided in this application embodiment can perform segmented control of the conduction process of the first switching transistor according to its operating characteristics at different stages of the conduction process. That is, different control methods are applied to the first switching transistor at different stages, thereby simultaneously reducing the conduction speed, current stress, and EMI of the first switching transistor.

[0172] Specifically, when the controller receives a high-level PWM signal for controlling the first switching transistor, it indicates that the first switching transistor has turned on. At this time, the first switching transistor switches from the off state to the on state, and the controller can first provide a fifth drive current to the gate of the first switching transistor to control the gate voltage of the first switching transistor to rise rapidly.

[0173] It is understandable that when the first switching transistor turns on, it is in a phase where rapid turn-on does not lead to EMI or current stress. Figure 3 The first and fourth stages are shown. Therefore, when the first switch turns on, the controller can provide a fifth drive current to the gate of the first switch to control the gate voltage of the first switch to rise rapidly, thereby accelerating the turn-on speed of the first switch and reducing the turn-on loss of the first switch.

[0174] Understandably, the power conversion device will provide different drive currents to the first switching transistor at different stages through the controller, resulting in different rates of increase in the gate voltage of the first switching transistor at different stages. For example, in... Figure 3 During the second and third stages shown, the controller is in a stage where current stress and EMI may occur. To this end, the controller can reduce the turn-on speed of the first switch in the second and third stages, thereby reducing the rise rate of the gate voltage of the first switch and avoiding the generation of large current stress and EMI.

[0175] In some feasible implementations, after the controller provides a fifth drive current to the gate of the first switch to control the rapid rise of the gate voltage of the first switch, the controller can further obtain the gate voltage of the first switch through a second voltage detection terminal, and when the gate voltage of the first switch is greater than or equal to a fourth threshold, provide a sixth drive current to the gate of the first switch to control the rate of increase of the gate voltage of the first switch to decrease. Here, the controller controlling the rate of increase of the gate voltage of the first switch to decrease means that the rate of increase of the gate voltage of the first switch is less than a first rate of increase, which is the rate of increase of the gate voltage of the first switch under the action of the fifth drive current.

[0176] It should be noted that rapid turn-off of the first switching transistor before its gate voltage is greater than or equal to the fourth threshold will not cause current stress or EMI. Figure 3 The first stage is shown. When the gate voltage of the first switch is greater than or equal to the fourth threshold, it indicates that the first switch has entered a stage where EMI and current stress may be significantly generated. Figure 3 The second and third stages are shown. Therefore, in order to reduce the current stress and EMI generation of the first switch, the controller can reduce the rate of increase of the gate voltage of the first switch to effectively reduce the current stress and EMI generation.

[0177] Specifically, when the controller detects that the gate voltage of the first switch is greater than or equal to the fourth threshold through the second voltage detection terminal, it can provide a sixth drive current to the gate of the first switch to reduce the rate of increase of the gate voltage of the first switch.

[0178] In some feasible implementations, such as Figure 3 As shown, in the second and third stages, the rapid turn-on of the first switch directly leads to EMI and current stress. However, in the subsequent fourth stage, the rapid turn-on of the first switch does not cause EMI or current stress. Therefore, in order to reduce current stress and EMI while accelerating the turn-on speed of the first switch to reduce its conduction loss, after the controller provides a sixth drive current to the gate of the first switch, the controller can obtain the voltage difference between the first and second electrodes of the first switch through the first voltage detection terminal. When the voltage difference between the first and second electrodes of the first switch is less than or equal to a fifth threshold, a seventh drive current is provided to the gate of the first switch to control the gate voltage of the first switch to rise rapidly until the gate voltage of the first switch is greater than or equal to the aforementioned turn-on threshold, i.e., the first switch is turned on.

[0179] It should be noted that the controller increases the gate voltage of the first switching transistor, which reduces the voltage difference between the first and second electrodes. Before the voltage difference between the first and second electrodes of the first switching transistor decreases to less than or equal to the fifth threshold, the first switching transistor is in a stage where EMI and current stress may occur significantly. Figure 3 The second and third stages are shown. When the voltage difference between the first and second electrodes of the first switching transistor is less than or equal to the fifth threshold, the rapid turn-on of the first switching transistor will not cause current stress or EMI. Figure 3 The fourth stage is shown.

[0180] In order to enable the first switch to turn on quickly and reduce the conduction loss of the first switch, the controller can provide a seventh drive current to the gate of the first switch when the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to the fifth threshold detected by the first voltage detection terminal. This controls the gate voltage of the first switch to rise rapidly until the gate voltage of the first switch is greater than or equal to the conduction threshold, that is, the first switch turns on.

[0181] To facilitate understanding of the process by which a power conversion device controls the first switching transistor to turn on via a controller, the following content combines... Figure 7 To illustrate, Figure 7 This is another waveform diagram of the first switching transistor provided in an embodiment of this application. Wherein, Figure 7 The PWM signal shown is the signal that controls the first switch to turn on. Vg is the gate voltage of the first switch, Ig is the drive current provided by the controller to the gate of the first switch (such as the fifth drive current, the sixth drive current or the seventh drive current mentioned above), and Vq is the voltage difference between the first electrode and the second electrode of the first switch.

[0182] It is understandable that, such as Figure 7 When time T0 arrives, the controller receives a high-level PWM signal to control the first switching transistor, indicating that the first switching transistor is on. At this time, the first switching transistor switches from the off state to the on state, and the controller can provide a fifth drive current Isc1 to the gate of the first switching transistor through the current control terminal to control the gate voltage Vg of the first switching transistor to rise from its minimum value Vsc0. The fifth drive current Isc1 is an upward current relative to the gate of the first switching transistor, meaning that the fifth drive current Isc1 can pull up the gate voltage of the first switching transistor. If combined with... Figure 4 As shown, the direction of the fifth driving current Isc1 is... Figure 4 The driving current Ig flows in the same direction. Furthermore, as the first switch begins to conduct, the voltage difference Vq between the first and second electrodes of the first switch begins to decrease.

[0183] At time T1, the controller detects that the gate voltage Vg of the first switch has risen to the fourth threshold Vsc1 via the first voltage detection terminal, indicating that the first switch has entered a stage where EMI and current stress may be generated significantly. To reduce the generation of current stress and EMI, the controller provides a sixth drive current Isc2 to the gate of the first switch via the current control terminal to control the rate of increase of the gate voltage Vg of the first switch to decrease. The sixth drive current Isc2 is a pull-up current relative to the gate of the first switch. Since the first switch is still not fully turned on, the voltage difference Vq between the first and second electrodes of the first switch will continue to decrease.

[0184] At time T2, the controller detects that the voltage difference Vq between the first and second electrodes of the first switching transistor has decreased to the fifth threshold Vf. At this point, the first switching transistor enters a stage where rapid turn-on will not cause significant EMI or current stress. To accelerate the turn-on speed and reduce the conduction losses of the first switching transistor, the controller provides a seventh drive current Isc3 to the gate of the first switching transistor through the current control terminal, thereby controlling the gate voltage Vg of the first switching transistor to rise rapidly from Vsc2. The seventh drive current Isc3 is a pull-up current relative to the gate of the first switching transistor.

[0185] Understandably, under the pull-up effect of the seventh drive current Isc3, the gate voltage of the first switch rapidly increases until it reaches the turn-on threshold Vsc3, at which point the first switch is fully turned on. At this time, the voltage difference Vq between the first electrode and the second electrode of the first switch is zero.

[0186] It should be noted that the specific methods for determining the values ​​of the fifth, sixth, and seventh drive currents, as well as the fourth and fifth thresholds, are not detailed here. Furthermore, the conduction process of the second switch connected in series with the first switch in the power conversion device can refer to the specific implementation method of the first switch described above; this application's embodiments will not elaborate further.

[0187] In some feasible implementations, in the power conversion device provided in the embodiments of this application, the controller can determine the magnitude of the fifth drive current based on the magnitude of the drive current provided to the gate of the first switch when controlling the first switch to turn on at a target turn-on speed.

[0188] As described above, when the first switch turns on, it signifies that the first switch has entered a stage where it can quickly turn on without causing EMI or current stress. At this time, the controller can provide a fifth drive current to the first switch, causing its gate voltage to rise rapidly. Therefore, the function of this fifth drive current is to quickly drive the gate voltage of the first switch to rise. To determine the magnitude of this fifth drive current, the controller can use multiple candidate drive currents as the gate drive current of the first switch to drive it through multiple turn-on tests. Furthermore, the controller can use one of the candidate drive currents used when the first switch reaches the target turn-on speed during these multiple turn-on tests as the fifth drive current.

[0189] It should be noted that the aforementioned target turn-on speed refers to the minimum turn-on speed of the first switching transistor to meet the switching rate requirements of the power conversion device. In other words, when the turn-on speed of the first switching transistor is greater than or equal to this target turn-on speed, the switching rate requirements of the power conversion device can be met without damaging the first switching transistor. Conversely, when the turn-on speed of the first switching transistor is less than this target turn-on speed, the switching rate requirements of the power conversion device are not met.

[0190] For example, suppose the controller uses Isc10, Isc11, and Isc12 as the aforementioned candidate drive currents. Further, when the controller provides candidate drive current Isc10 to the gate of the first switch to drive it to turn on, it obtains a turn-on speed of v0 for the first switch. When the controller provides candidate drive current Isc11 to the gate of the first switch to drive it to turn on, it obtains a turn-on speed of v1 for the first switch. When the controller provides candidate drive current Isc12 to the gate of the first switch to drive it to turn on, it obtains a turn-off speed of v2 for the first switch. Now, suppose the target turn-on speed of the first switch is vb, and v0 < v1 < vb < v2. Therefore, when the controller provides candidate drive current Isc12 to the gate of the first switch to drive it to turn on, the turn-on speed of the first switch is greater than the turn-on speed when other candidate drive currents are provided to drive it to turn off, and is greater than or equal to the target turn-on speed vb. Meanwhile, when the controller drives the first switch to conduct with the candidate drive current, it will not damage the first switch. Therefore, the controller can use the candidate drive current Isc12 as the fifth drive current of the first switch.

[0191] In some feasible implementations, in the power conversion device provided in the embodiments of this application, the controller can determine the magnitude of the seventh drive current based on the magnitude of the drive current provided to the gate of the first switch when controlling the first switch to turn on at a target turn-off speed.

[0192] It should be noted that the specific implementation of the controller determining the magnitude of the seventh drive current can refer to the specific implementation of determining the magnitude of the fifth drive current described above, and will not be repeated in this application embodiment. Furthermore, the magnitudes of the fifth drive current and the seventh drive current can be the same or different, and this application embodiment does not limit this.

[0193] In some feasible implementations, the controller may determine the magnitude of the fifth threshold based on the following:

[0194] As described above, in this embodiment, the power conversion device controls the first switching transistor to turn on via a controller, aiming to reduce the conduction loss of the first switching transistor and simultaneously reduce the current stress and EMI generated during the conduction process. To this end, the power conversion device can use multiple voltage thresholds as candidate voltage thresholds to detect the current stress and EMI generated by the first switching transistor when these candidate voltage thresholds are applied during its conduction process, thereby determining the optimal voltage threshold as the aforementioned fifth threshold.

[0195] Specifically, since the voltage across the first switching transistor can be equal to the operating voltage of the bus during conduction, the value of the fifth threshold can range from the operating voltage of the bus to zero. Therefore, the controller can obtain multiple voltage thresholds as candidate voltage thresholds based on the operating voltage of the bus. For example, the controller can use 1 / N to (N-1) / N of the operating voltage of the bus as the multiple voltage thresholds, where N is a positive integer greater than 1.

[0196] Understandably, the controller can use a voltage threshold as a candidate voltage threshold and, while providing the aforementioned sixth drive current to the gate of the first switch, obtain the voltage difference between the first and second electrodes of the first switch through the first voltage detection terminal. When the controller detects that the voltage difference is less than or equal to the candidate voltage threshold, it provides a seventh drive current to the gate of the first switch until the first switch is fully turned on. Furthermore, the controller iterates through the aforementioned multiple voltage thresholds, that is, it uses each voltage threshold as a candidate voltage threshold and controls the first switch to perform multiple full-turn-on tests.

[0197] Meanwhile, to compare the current stress and EMI generated by the first switching transistor during multiple turn-on processes, the controller can acquire the current amplitude flowing through the first and second electrodes of the first switching transistor during each turn-on process. The variation of this current amplitude can be used to characterize the current stress and EMI generated by the first switching transistor. For example, the current amplitude of the first switching transistor can be as follows: Figure 6 As shown in the figure, the smaller the peak value of the current amplitude Is of the first switch, the less current stress and EMI generated by the first switch can be considered.

[0198] Therefore, the controller can obtain the current stress and EMI generated by the first switching transistor under different voltage threshold control by using the current amplitude corresponding to multiple voltage thresholds obtained from multiple full conduction tests. Furthermore, the controller can determine the voltage threshold corresponding to the minimum current stress and EMI generated by the first switching transistor as the aforementioned fifth threshold.

[0199] It should be noted that the methods for determining the first and second thresholds can also refer to the specific implementation of the fifth threshold, and this application will not elaborate on this aspect.

[0200] In this embodiment, when the first switch is turned on, the power conversion device controls the gate voltage of the first switch to rise via a controller. When the gate voltage of the first switch is greater than or equal to a fourth threshold, the device controls the rate of increase of the gate voltage to decrease, effectively reducing current stress and EMI generation. Furthermore, when the voltage difference across the first switch is less than or equal to a fifth threshold, the power conversion device controls the rate of increase of the gate voltage of the first switch to increase via a controller until the first switch is fully turned on. This reduces current stress and EMI generation while increasing the turn-on speed of the first switch, thereby reducing conduction losses.

[0201] Please see Figure 8 , Figure 8 This is a flowchart illustrating a control method for a power conversion device provided in this application. The control method for a power conversion device provided in this application is applicable to... Figures 1 to 7 The controller shown. Specifically, the control method for the power conversion device may include the following steps:

[0202] S101. When the turn-off time of the first switch arrives, a first drive current is provided to the gate of the first switch to control the gate voltage of the first switch to decrease, and when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a first threshold, a second drive current is provided to the gate of the first switch to control the gate voltage of the first switch to increase.

[0203] It should be noted that when the first switch turns off, the power conversion device provides a first drive current to the gate of the first switch through the controller to control the gate voltage of the first switch to drop. When the voltage difference across the first switch, i.e. the voltage difference between the first electrode and the second electrode, reaches a first threshold, the controller provides a second drive current to the gate of the first switch to control the gate voltage of the first switch to rise. This can effectively reduce voltage stress and EMI generation.

[0204] For a detailed implementation of S101, please refer to the above. Figures 1 to 7 The implementation method executed by the controller is not described in detail in this application embodiment.

[0205] S102. When a second drive current is provided to the gate of the first switch, when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a second threshold, or when the duration of providing the second drive current to the gate of the first switch is greater than or equal to a time threshold, a third drive current is provided to the gate of the first switch to control the gate voltage of the first switch to decrease until the first switch is turned off.

[0206] It should be noted that, in the power conversion device, the voltage difference across the first switching transistor, i.e., the voltage difference between the first electrode and the second electrode, is greater than or equal to the second threshold. Alternatively, when the duration of the controller providing the second drive current to the gate of the first switching transistor is greater than or equal to the time threshold, the controller provides a third drive circuit to the gate of the first switching transistor to control the gate voltage of the first switching transistor to change from rising to falling until the first switching transistor is completely turned off. This can reduce voltage stress and EMI generation while improving the turn-off speed of the first switching transistor, thereby reducing turn-off losses.

[0207] For a detailed implementation of S102, please refer to the above. Figures 1 to 7 The implementation method executed by the controller is not described in detail in this application embodiment.

[0208] In an optional embodiment, the method further includes: when a first drive current is provided to the gate of the first switch, obtaining the gate voltage of the first switch, and when the gate voltage of the first switch is less than or equal to a third threshold, providing a fourth drive current to the gate of the first switch, so as to control the rate of decrease of the gate voltage of the first switch to be less than a first rate of decrease, wherein the first rate of decrease is the rate of decrease of the gate voltage of the first switch when the first drive current is provided to the gate of the first switch.

[0209] It is understandable that after the power conversion device provides the first drive current to the gate of the first switch, it can obtain the gate voltage of the first switch through the controller. When the gate voltage of the first switch is less than or equal to the third threshold, the controller controls the rate of decrease of the gate voltage of the first switch to decrease. In this way, while reducing voltage stress and EMI generation, the turn-off speed of the first switch can be further improved, effectively reducing turn-off losses.

[0210] In an optional implementation, the method includes: obtaining the magnitude of a first drive current and the magnitude of a third drive current based on the gate drive current used to control the first switch to turn off at a target turn-off speed.

[0211] Understandably, the power conversion device can obtain the magnitudes of the first drive current and the third drive current based on the gate drive current corresponding to the target turn-off speed through the controller. Furthermore, when driving the first switch based on the first drive current or the third drive current, the gate voltage of the first switch can drop rapidly, thereby further improving the turn-off speed of the first switch and effectively reducing turn-off losses.

[0212] In an optional implementation, the method includes: after providing a first drive current to the gate of a first switch, detecting the rate of change of the voltage difference between a first electrode and a second electrode of the first switch, and obtaining the magnitude of a second drive current based on the detected rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

[0213] Understandably, when the controller drives the first switching transistor based on the second drive current, it can increase the gate voltage of the first switching transistor to reduce voltage stress and EMI generation. The controller obtains the magnitude of the second drive current based on the rate of change of the voltage difference between the first and second electrodes of the first switching transistor, which is easy to implement and highly accurate.

[0214] In an optional embodiment, the method includes: after providing a first drive current to the gate of a first switch, detecting the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from a first voltage difference to a second voltage difference, and obtaining the magnitude of a second drive current based on the detected time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

[0215] Understandably, when the controller drives the first switching transistor based on the second drive current, it can increase the gate voltage of the first switching transistor to reduce voltage stress and EMI generation. Specifically, the controller obtains the magnitude of the second drive current based on the time it takes for the voltage difference between the first and second electrodes of the first switching transistor to increase from a first voltage difference to a second voltage difference; this method is easy to implement and highly accurate.

[0216] In an optional implementation, the method includes: when a second drive current is provided to the gate of the first switch, adjusting the magnitude of the second drive current based on the rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

[0217] It is understandable that after the controller provides the second drive current to the first switching transistor, it can adjust the magnitude of the second drive current based on the rate of change of the voltage difference between the first and second electrodes of the first switching transistor, thereby effectively reducing voltage stress and EMI generation. This is easy to implement and can be adjusted in real time.

[0218] In an optional embodiment, the method includes: when a second drive current is provided to the gate of the first switch, adjusting the magnitude of the second drive current based on the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from a first voltage difference to a second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

[0219] It is understandable that after the controller provides the second drive current to the first switching transistor, it can adjust the magnitude of the second drive current based on the time it takes for the voltage difference between the first and second electrodes of the first switching transistor to increase from the first voltage difference to the second voltage difference, thereby effectively reducing voltage stress and EMI generation. This is easy to implement and can be adjusted in real time.

[0220] In an optional implementation, the method includes: after providing a first drive current to the gate of a first switch, detecting the rate of change of the voltage difference between a first electrode and a second electrode of the first switch, and obtaining a time threshold based on the detected rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

[0221] It is understandable that after the controller provides the first drive current to the first switching transistor, it can determine the value of the above-mentioned time threshold based on the rate of change of the voltage difference between the first electrode and the second electrode of the first switching transistor, which is easy to implement and has high accuracy.

[0222] In an optional embodiment, the method includes: after providing a first drive current to the gate of a first switch, detecting the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from a first voltage difference to a second voltage difference, and obtaining a time threshold based on the detected time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference; wherein the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

[0223] It is understandable that after the controller provides the first drive current to the first switching transistor, it can determine the value of the above-mentioned time threshold based on the time length of time it takes for the voltage difference between the first electrode and the second electrode of the first switching transistor to increase from the first voltage difference to the second voltage difference. This is easy to implement and has high accuracy.

[0224] In an optional embodiment, the method further includes: when the first switch is turned on, providing a fifth drive current to the gate of the first switch to control the gate voltage of the first switch to rise; and when the gate voltage of the first switch is greater than or equal to a fourth threshold, providing a sixth drive current to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be less than a first rise rate, wherein the first rise rate is the rise rate of the gate voltage of the first switch when the fifth drive current is provided to the gate of the first switch; when the sixth drive current is provided to the gate of the first switch, when the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to the fifth threshold, providing a seventh drive current to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be greater than a second rise rate, until the first switch is turned on; wherein the second rise rate is the rise rate of the gate voltage of the first switch when the sixth drive current is provided to the gate of the first switch, and the fifth threshold is less than the operating voltage of the bus.

[0225] Understandably, when the first switch is turned on, the power conversion device controls the gate voltage of the first switch to rise via a controller. When the gate voltage reaches or exceeds a fourth threshold, the rate of rise of the gate voltage decreases, effectively reducing current stress and EMI. Furthermore, when the voltage difference across the first switch is less than or equal to a fifth threshold, the power conversion device controls the rate of rise of the gate voltage to increase until the first switch is fully turned on. This reduces current stress and EMI while simultaneously increasing the turn-on speed of the first switch, thereby reducing conduction losses.

[0226] In an alternative implementation, the method includes: obtaining the magnitude of a fifth drive current and the magnitude of a seventh drive current based on the gate drive current used to control the first switch to turn on at a target turn-on speed.

[0227] Understandably, the controller can obtain the magnitudes of the fifth and seventh drive currents based on the gate drive current corresponding to the target turn-on speed. Furthermore, when the controller drives the first switch based on the fifth or seventh drive current, it can cause the gate voltage of the first switch to rise rapidly, thereby further improving the turn-on speed of the first switch and effectively reducing turn-off losses.

[0228] In an optional embodiment, the method further includes: obtaining multiple voltage thresholds based on the operating voltage of the bus, wherein the voltage thresholds are less than the operating voltage of the bus; when a sixth drive current is provided to the gate of the first switch, traversing the multiple voltage thresholds to use each voltage threshold as a candidate voltage threshold, and when the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to the candidate voltage threshold, providing a seventh drive current to the gate of the first switch to control the gate voltage of the first switch to rise until the first switch is turned on; obtaining the current amplitude of the first electrode and the second electrode corresponding to the candidate voltage threshold during the turn-on process of the first switch, so as to obtain the current amplitude of the first electrode and the second electrode corresponding to each voltage threshold; and determining a fifth threshold from the multiple voltage thresholds based on the current amplitude of the first electrode and the second electrode corresponding to each voltage threshold.

[0229] Understandably, the controller can use a voltage threshold as a candidate voltage threshold and, while providing the aforementioned sixth drive current to the gate of the first switch, obtain the voltage difference between the first and second electrodes of the first switch through the first voltage detection terminal. When the controller detects that the voltage difference is less than or equal to the candidate voltage threshold, it provides a seventh drive current to the gate of the first switch until the first switch is fully turned on. Furthermore, the controller iterates through the aforementioned multiple voltage thresholds, that is, it uses each voltage threshold as a candidate voltage threshold and controls the first switch to perform multiple full-turn-on tests.

[0230] Simultaneously, during each conduction process, the controller can acquire the current amplitude flowing through the first and second electrodes of the first switching transistor. The variation of this current amplitude can be used to characterize the current stress and EMI generated by the first switching transistor. The controller can obtain the current stress and EMI generated by the first switching transistor under different voltage threshold controls by acquiring the current amplitude corresponding to multiple voltage thresholds obtained from multiple full conduction tests. Furthermore, the controller can identify the voltage threshold corresponding to the minimum current stress and EMI generated by the first switching transistor under different voltage thresholds as the aforementioned fifth threshold.

[0231] Based on the same concept, this application also provides a switch driver chip, which includes the controller in the aforementioned power conversion device. The switch driver chip can be connected to a first switch and a second switch, respectively, and the first and second switches can be turned on or off. Specific implementations of the above-described switch driver chip can be found in the above-described... Figures 1 to 8 The implementation method executed by the controller is not described in detail in this application embodiment.

[0232] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0233] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0234] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0235] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0236] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the scope of protection of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A power conversion device, characterized in that, The power conversion device includes a controller, a first switch and a second switch connected in series; the gate of the first switch is connected to the controller, the first electrode of the first switch is connected to the second switch, and the second electrode of the first switch is grounded or connected to a bus. The controller is used for: When the turn-off time of the first switch arrives, a first drive current is provided to the gate of the first switch to control the gate voltage of the first switch to decrease, and when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a first threshold, a second drive current is provided to the gate of the first switch to control the gate voltage of the first switch to increase. When the second drive current is provided to the gate of the first switch, when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a second threshold, or when the duration of providing the second drive current to the gate of the first switch is greater than or equal to a time threshold, a third drive current is provided to the gate of the first switch to control the gate voltage of the first switch to decrease until the first switch is turned off.

2. The power conversion device according to claim 1, characterized in that, The controller is used for: When the first drive current is provided to the gate of the first switch, the gate voltage of the first switch is obtained, and when the gate voltage of the first switch is less than or equal to a third threshold, a fourth drive current is provided to the gate of the first switch to control the rate of decrease of the gate voltage of the first switch to be less than a first rate of decrease, wherein the first rate of decrease is the rate of decrease of the gate voltage of the first switch when the first drive current is provided to the gate of the first switch.

3. The power conversion device according to claim 1 or 2, characterized in that, The controller is used for: The magnitudes of the first drive current and the third drive current are obtained based on the gate drive current used to control the first switch to turn off at the target turn-off speed.

4. The power conversion device according to any one of claims 1-3, characterized in that, The controller is used for: After providing the first drive current to the gate of the first switch, the rate of change of the voltage difference between the first electrode and the second electrode of the first switch is detected, and the magnitude of the second drive current is obtained based on the detected rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

5. The power conversion device according to any one of claims 1-3, characterized in that, The controller is used for: After providing the first drive current to the gate of the first switch, the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference is detected, and the magnitude of the second drive current is obtained based on the detected time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference. Wherein, the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

6. The power conversion device according to any one of claims 1-3, characterized in that, The controller is used for: When the second drive current is supplied to the gate of the first switch, the magnitude of the second drive current is adjusted based on the rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

7. The power conversion device according to any one of claims 1-3, characterized in that, The controller is used for: When the second drive current is provided to the gate of the first switch, the magnitude of the second drive current is adjusted based on the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference. Wherein, the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

8. The power conversion device according to any one of claims 1-7, characterized in that, The controller is used for: After providing the first drive current to the gate of the first switch, the rate of change of the voltage difference between the first electrode and the second electrode of the first switch is detected, and the time threshold is obtained based on the detected rate of change of the voltage difference between the first electrode and the second electrode of the first switch.

9. The power conversion device according to any one of claims 1-7, characterized in that, The controller is used for: After providing the first drive current to the gate of the first switch, the time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference is detected, and the time threshold is obtained based on the detected time length during which the voltage difference between the first electrode and the second electrode of the first switch increases from the first voltage difference to the second voltage difference. Wherein, the first voltage difference and the second voltage difference are less than the operating voltage of the bus.

10. The power conversion device according to any one of claims 1-9, characterized in that, The controller is used for: When the first switch is turned on, a fifth drive current is provided to the gate of the first switch to control the gate voltage of the first switch to rise. When the gate voltage of the first switch is greater than or equal to a fourth threshold, a sixth drive current is provided to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be less than a first rise rate, where the first rise rate is the rise rate of the gate voltage of the first switch when the fifth drive current is provided to the gate of the first switch. When the sixth drive current is provided to the gate of the first switch, and the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to a fifth threshold, a seventh drive current is provided to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be greater than a second rise rate until the first switch is turned on; wherein, the second rise rate is the rise rate of the gate voltage of the first switch when the sixth drive current is provided to the gate of the first switch, and the fifth threshold is less than the operating voltage of the bus.

11. The power conversion device according to claim 10, characterized in that, The controller is used for: The magnitudes of the fifth drive current and the seventh drive current are obtained based on the gate drive current used to control the first switch to turn on at the target turn-on speed.

12. A control method for a power conversion device, characterized in that, The power conversion device includes a first switch and a second switch connected in series; the first electrode of the first switch is connected to the second switch, and the second electrode of the first switch is grounded or connected to a bus. The method includes: When the turn-off time of the first switch arrives, a first drive current is provided to the gate of the first switch to control the gate voltage of the first switch to decrease, and when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a first threshold, a second drive current is provided to the gate of the first switch to control the gate voltage of the first switch to increase. When the second drive current is provided to the gate of the first switch, when the voltage difference between the first electrode and the second electrode of the first switch is greater than or equal to a second threshold, or when the duration of providing the second drive current to the gate of the first switch is greater than or equal to a time threshold, a third drive current is provided to the gate of the first switch to control the gate voltage of the first switch to decrease until the first switch is turned off.

13. The control method according to claim 12, characterized in that, The method further includes: When the first switch is turned on, a fifth drive current is provided to the gate of the first switch to control the gate voltage of the first switch to rise. When the gate voltage of the first switch is greater than or equal to a fourth threshold, a sixth drive current is provided to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be less than a first rise rate, where the first rise rate is the rise rate of the gate voltage of the first switch when the fifth drive current is provided to the gate of the first switch. When the sixth drive current is provided to the gate of the first switch, and the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to a fifth threshold, a seventh drive current is provided to the gate of the first switch to control the rise rate of the gate voltage of the first switch to be greater than a second rise rate until the first switch is turned on; wherein, the second rise rate is the rise rate of the gate voltage of the first switch when the sixth drive current is provided to the gate of the first switch, and the fifth threshold is less than the operating voltage of the bus.

14. The control method according to claim 13, characterized in that, The method further includes: Multiple voltage thresholds are obtained based on the operating voltage of the bus, wherein the voltage thresholds are less than the operating voltage of the bus; When the sixth drive current is provided to the gate of the first switch, the plurality of voltage thresholds are traversed to take each of the voltage thresholds as a candidate voltage threshold, and when the voltage difference between the first electrode and the second electrode of the first switch is less than or equal to the candidate voltage threshold, a seventh drive current is provided to the gate of the first switch to control the gate voltage of the first switch to rise until the first switch is turned on. The current amplitudes of the first electrode and the second electrode corresponding to the candidate voltage threshold are obtained during the conduction process of the first switch, so as to obtain the current amplitudes of the first electrode and the second electrode corresponding to each voltage threshold. The fifth threshold is determined from the plurality of voltage thresholds based on the current amplitudes of the first electrode and the second electrode corresponding to each of the voltage thresholds.

15. A switch driver chip, characterized in that, The switch driver chip includes a controller as described in any one of claims 1 to 11, and the switch driver chip is connected to a first switch transistor and a second switch transistor. The switch driver chip is used to drive the first switch to turn on or off, and to drive the second switch to turn on or off.

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