Negative pressure control circuit and negative pressure control method

Abstract

The application provides a negative voltage control circuit and a negative voltage control method. The circuit comprises a gate drive circuit, a negative voltage regulating circuit, a control circuit and a power switching device. The control circuit is used for outputting a control signal, and the control signal is used for indicating the off or on of the power switching device. The gate drive circuit is connected between the control circuit and the power switching device, used for receiving the control signal, and switching the voltage type of the gate voltage of the power switching device according to the control signal. The negative voltage regulating circuit is connected with the gate drive circuit and the power switching device, used for collecting the output current of the power switching device, and regulating the negative voltage applied to the gate drive circuit according to the output current. The circuit solves the problem that the power switching device is controlled by the fixed negative voltage in the prior art, and the power switching device cannot be turned off due to the Miller effect.

Description

Technical Field

[0001] This invention relates to the field of circuit control technology, and more specifically, to a negative pressure control circuit and a negative pressure control method. Background Technology

[0002] Power switching devices (such as IGBTs) are widely used in motor drives, converters, rectifiers and other control scenarios. However, for frequency converters or servo drives, power switching devices will frequently turn on and off. If they are not turned off in time, they may cause transistors to explode or even burn out the circuit.

[0003] In order to ensure the turn-off response speed, negative voltage is usually used for control in the existing technology. Specifically, when the power switching device needs to be turned off, a negative voltage is applied to its gate circuit to achieve a fast response. At the same time, it can also avoid false turn-on caused by Miller capacitance.

[0004] However, existing negative pressure control technologies typically employ a fixed negative pressure. Since the fixed negative pressure is based on empirical settings, it is difficult to guarantee the accuracy of the negative pressure. If the negative pressure is too low, it will increase the losses of the power switching devices and may even damage them. If the negative pressure is close to 0, it will have little effect on the turn-off process and in addressing the Miller effect. Summary of the Invention

[0005] The main objective of this application is to provide a negative pressure control circuit and a negative pressure control method to at least solve the problem in the prior art where power switching devices are controlled by a fixed negative pressure and are prone to failure to turn off due to the Miller effect.

[0006] To achieve the above objectives, according to one aspect of this application, a negative voltage control circuit is provided. The negative voltage control circuit includes a gate drive circuit, a negative voltage regulation circuit, a control circuit, and a power switching device. The control circuit outputs a control signal to indicate whether the power switching device is turned off or on. The gate drive circuit is connected between the control circuit and the power switching device, and receives the control signal to switch the voltage type of the gate voltage of the power switching device according to the control signal. The negative voltage regulation circuit is connected to the gate drive circuit and the power switching device, and acquires the output current of the power switching device to adjust the negative voltage applied to the gate drive circuit according to the output current.

[0007] Optionally, the negative voltage regulation circuit includes: a current acquisition circuit connected to the power switching device for acquiring the output current of the power switching device; an operational amplifier circuit connected to the current acquisition circuit and the gate drive circuit for adjusting the negative voltage applied to the gate drive circuit according to the output current; and a clamping circuit connected to the operational amplifier circuit for reducing the gate voltage of the power switching device to the reference potential when the absolute value of the negative voltage output by the operational amplifier circuit exceeds the reference voltage.

[0008] Optionally, the current acquisition circuit includes: a first current sensor connected to the drain of the power switching device for acquiring the drain current of the power switching device; and a second current sensor connected to the source of the power switching device for acquiring the source current of the power switching device.

[0009] Optionally, the operational amplifier circuit includes: an operational amplifier for generating a negative voltage signal based on the current difference between the drain current and the source current; a scaling circuit connected between the current acquisition circuit and the operational amplifier for adjusting the negative voltage signal output by the operational amplifier; and a voltage divider circuit connected to the output terminal of the operational amplifier for scaling the negative voltage signal.

[0010] Optionally, the clamping circuit includes: a first switching transistor for reducing the gate voltage of the power switching device to a reference potential; and a comparator, wherein the inverting input of the comparator is connected to the output of the operational amplifier, and the non-inverting input of the comparator is connected to a reference voltage source, and the comparator is used to control the on / off state of the first switching transistor.

[0011] Optionally, the voltage divider circuit includes a first resistor and a second resistor, wherein the first end of the first resistor is connected to the output terminal of the operational amplifier, the second end of the first resistor is connected to the first end of the second resistor, the second end of the second resistor is connected to a preset negative voltage, and the connection point of the first resistor and the second resistor is connected to the gate drive circuit.

[0012] Optionally, the operational amplifier circuit also includes a clamping transistor, the cathode of which is connected to the junction of the first resistor and the second resistor, and the anode of which is connected to a preset negative voltage. The clamping transistor is used to limit the negative voltage at the preset voltage when the negative voltage output at the junction exceeds the preset voltage.

[0013] Optionally, the scaling circuit includes a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The third resistor is connected between the non-inverting input of the operational amplifier and the first current sensor. The fourth resistor is connected between the inverting input of the operational amplifier and the second current sensor. The first end of the fifth resistor is connected to the inverting input of the operational amplifier, and the second end of the fifth resistor is grounded. The first end of the sixth resistor is connected between the third resistor and the non-inverting input of the operational amplifier, and the second end of the sixth resistor is connected to the output of the operational amplifier. The third, fourth, fifth, and sixth resistors are used to control the scaling ratio of the operational amplifier.

[0014] Optionally, the gate drive circuit includes: a second switch connected to the control circuit, which turns on upon receiving a turn-on control signal from the control circuit; a third switch connected to the control circuit, which turns on upon receiving a turn-off control signal from the control circuit; a positive voltage isolation diode connected between the second switch and the power switching device, used to prevent positive voltage injection into the negative voltage regulation circuit when the second switch is on; a negative voltage isolation diode connected between the third switch and the power switching device, used to prevent negative voltage interference when the third switch is on; a seventh resistor connected between the positive voltage isolation diode and the power switching device, used to limit the gate charging current of the power switching device; and an eighth resistor connected between the negative voltage isolation diode and the power switching device, used to limit the discharge rate of the power switching device.

[0015] According to another aspect of this application, a negative voltage control method is provided, which is applied to any of the above-mentioned negative voltage control circuits. The negative voltage control method includes: acquiring the source current of a power switching device and acquiring the drain current of the power switching device; calculating the difference between the drain current and the source current to obtain a current difference; and adjusting the gate turn-off negative voltage of the power switching device according to the polarity of the current difference.

[0016] Optionally, adjusting the gate turn-off negative voltage of the power switching device according to the polarity of the current difference includes: increasing the gate turn-off negative voltage when the current difference is greater than 0; and decreasing the gate turn-off negative voltage when the current difference is less than 0.

[0017] According to the technical solution of this application, the aforementioned negative voltage control circuit includes a gate drive circuit, a negative voltage adjustment circuit, a control circuit, and a power switching device. The control circuit outputs a control signal to indicate whether the power switching device is turned off or on. The gate drive circuit, connected between the control circuit and the power switching device, receives the control signal and switches the gate voltage type of the power switching device according to the control signal. The negative voltage adjustment circuit, connected to the gate drive circuit and the power switching device, acquires the output current of the power switching device and adjusts the negative voltage applied to the gate drive circuit according to the output current. This application, through the negative voltage adjustment circuit, adjusts the gate turn-off negative voltage of the power switching device based on the output current of the source and drain of the power switching device, ensuring the immediate response of the power switching device to the control signal. This solves the problem in the prior art where a fixed negative voltage is used to control the power switching device, which easily leads to failure to turn off due to the Miller effect. Attached Figure Description

[0018] Figure 1 A circuit diagram of a negative pressure control circuit provided in an embodiment of this application is shown;

[0019] Figure 2 A driving circuit diagram of a prior art power switching device is shown according to an embodiment of this application;

[0020] Figure 3 A current flow diagram during conduction is shown according to an embodiment of this application;

[0021] Figure 4 A current flow diagram during shutdown is shown according to an embodiment of this application;

[0022] Figure 5 A schematic flowchart of a negative pressure control method according to an embodiment of this application is shown. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0026] As described in the background section, existing negative pressure control typically employs a fixed negative pressure. However, since the fixed negative pressure is based on empirical settings, it is difficult to guarantee the accuracy of the negative pressure. If the negative pressure is too low, it will increase the losses of the power switching devices and may even damage them. If the negative pressure is close to 0, it will have little effect on the turn-off process and in addressing the Miller effect. To solve the problem that existing technologies using fixed negative pressure to control power switching devices are prone to failure to turn off due to the Miller effect, embodiments of this application provide a negative pressure control circuit and a negative pressure control method.

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0028] In one embodiment of this application, such as Figure 1 As shown, a negative voltage control circuit is provided. This negative voltage control circuit includes a gate drive circuit, a negative voltage adjustment circuit, a control circuit, and a power switching device.

[0029] The control circuit is used to output control signals, which are used to indicate whether the power switching device is turned off or on.

[0030] Specifically, such as Figure 1 As shown, the control circuit, namely the drive controller U1, is used to output a turn-on or turn-off command signal according to the system operation requirements. It can be understood that this signal is a digital level signal. This digital level signal does not directly act on the power switching device, but is transmitted to the gate drive circuit as a trigger signal. The gate drive circuit controls the power switching device Q3 by responding to the trigger signal.

[0031] The gate drive circuit is connected between the control circuit and the power switching device. It is used to receive control signals and switch the voltage type of the gate voltage of the power switching device according to the control signals.

[0032] Specifically, the gate drive circuit is located between the control circuit and the power switching device, and plays the role of signal conversion and energy transfer. It can be understood that the gate drive circuit responds to the trigger signal of the control circuit and applies positive and negative voltages to the gate circuit of the power switching device by turning on and off different internal switching transistors. Specifically, a positive drive voltage is applied when the trigger signal is on and a negative voltage is applied when the trigger signal is off.

[0033] The negative voltage regulation circuit is connected to the gate drive circuit and the power switching device. It is used to collect the output current of the power switching device and adjust the negative voltage applied to the gate drive circuit according to the output current.

[0034] Specifically, the aforementioned negative voltage regulation circuit is directly connected to the source and drain of the power switching device, collects its operating current, and generates a negative voltage output that matches the current state in real time through analog calculation. Compared with the fixed-level switch with fixed negative voltage in the prior art, this application uses variable level execution. Although the voltage type (positive or negative) of the gate voltage is still determined by the control circuit, the amplitude of the negative voltage is regulated by the negative voltage regulation circuit to ensure that the negative voltage applied to the gate circuit can accurately turn off the power switching device and avoid damage to the components or failure to turn off.

[0035] In the above embodiments, the negative voltage control circuit includes a gate drive circuit, a negative voltage adjustment circuit, a control circuit, and a power switching device. The control circuit outputs a control signal to indicate whether the power switching device is turned off or on. The gate drive circuit, connected between the control circuit and the power switching device, receives the control signal and switches the gate voltage type of the power switching device according to the control signal. The negative voltage adjustment circuit, connected to the gate drive circuit and the power switching device, acquires the output current of the power switching device and adjusts the negative voltage applied to the gate drive circuit according to the output current. This application, through the negative voltage adjustment circuit, adjusts the gate turn-off negative voltage of the power switching device based on the output current of the source and drain of the power switching device, ensuring the immediate response of the power switching device to the control signal. This solves the problem in the prior art where a fixed negative voltage is used to control the power switching device, which easily leads to failure to turn off due to the Miller effect.

[0036] In one optional embodiment of this application, the negative pressure regulating circuit includes:

[0037] The current acquisition circuit is connected to the power switching device and is used to acquire the output current of the power switching device.

[0038] Specifically, the current acquisition circuit is directly connected to the drain and source of the power switching device, acquiring the drain current and source current flowing through the device, respectively. Understandably, when the power switching device is normally on, the drain current and source current are essentially equal, with the current difference approaching zero. However, during the turn-off process, due to the coupling effect of the Miller capacitance inside the device, the drain voltage rises rapidly, but the drain current maintains a residual value for a certain period. Meanwhile, the source current decreases first due to the load circuit characteristics, resulting in a significant difference between the two. This difference reflects the formation and strength of the Miller plateau, guiding subsequent adjustments to the negative voltage amplitude to eliminate the Miller effect.

[0039] An operational amplifier circuit, connected to a current acquisition circuit and a gate drive circuit, is used to adjust the negative voltage applied to the gate drive circuit according to the output current.

[0040] Specifically, the operational amplifier circuit receives two current signals from the current acquisition circuit, converts them into voltage signals, performs differential calculations, and outputs a control voltage proportional to the current difference. Understandably, this circuit uses a precision resistor network to set the gain and bias, causing the output voltage to increase linearly with the increase of the current difference, thereby driving subsequent negative voltage regulation.

[0041] Specifically, when the current difference is zero or very small (on-state or steady state), the output voltage of the above-mentioned operational amplifier circuit approaches zero, and the negative voltage automatically approaches 0V, minimizing turn-on losses; when the current difference gradually increases (mid-turn-off stage), the output voltage rises, and the negative voltage increases synchronously, ensuring that the gate is sufficiently pulled low to suppress Miller rise; when the current difference reaches its peak value (Miller spike), the output voltage rises rapidly to the preset limit, providing conditions for triggering the clamping circuit.

[0042] Through the above settings, the negative pressure can be continuously adjusted according to the actual physical state of the power switching device. Compared with the fixed negative pressure control in the prior art, this avoids the damage caused by excessive negative pressure and the problem of false circuit caused by insufficient negative pressure.

[0043] A clamping circuit, connected to an operational amplifier circuit, is used to reduce the gate voltage of the power switching device to the reference potential when the absolute value of the negative voltage output by the operational amplifier circuit exceeds the reference voltage.

[0044] Specifically, when the operational amplifier output voltage exceeds a set threshold, the gate voltage is forcibly clamped to a safe reference potential.

[0045] Through the above embodiments, the circuit constitutes a closed-loop adaptive negative voltage regulation circuit, which adjusts the negative voltage amplitude according to the state of the power switch tube, thus solving the problem of circuit damage caused by misleading conduction due to Miller effect and negative voltage mismatch in the prior art.

[0046] In one optional embodiment of this application, the above-mentioned current acquisition circuit includes:

[0047] The first current sensor is connected to the drain of the power switching device and is used to collect the drain current of the power switching device.

[0048] Specifically, such as Figure 1 As shown, the first current sensor U4 is installed on the drain side of the power switching device. Its function is to acquire the drain current flowing through the main path of the device in real time, which serves as one of the physical bases for subsequent negative voltage regulation.

[0049] Understandably, at the instant a power switching device is turned on, the drain current rises rapidly. At this time, the gate voltage is driven by a positive voltage, and the current path is mainly power supply → drain → channel → source → ground. This current reflects the device's conduction state and the load size. In the initial turn-off phase, although the drain current begins to decrease, due to the Miller effect, the gate capacitance is reverse-charged, causing the gate potential to rise. At this time, the drain current still maintains a certain amplitude, forming a Miller plateau. If a constant negative voltage is maintained at this point, excessive strength will cause losses to the power switching transistor, while insufficient strength will lead to mis-turn-on.

[0050] The second current sensor is connected to the source of the power switching device and is used to collect the source current of the power switching device.

[0051] Specifically, such as Figure 1 As shown, the second current sensor U5 is installed on the source side of the power switching device to collect the source current. Under normal conduction conditions, the source current and drain current are basically equal (ignoring the small gate charging current); however, during the turn-off process, due to the Miller effect of the gate capacitance, there is a plateau, causing the source current to drop first, while the drain current remains at a higher level due to the freewheeling effect of the inductive load.

[0052] It is understandable that the instantaneous deviation between the source current and drain current during the turn-off process can be used as an electrical identification feature of the Miller effect.

[0053] In the above embodiments, current sensors are set at the source and drain terminals respectively to synchronously collect the source current and drain current, forming a current deviation, which is used to identify whether the Miller effect occurs, and serves as the basis for subsequent negative pressure regulation.

[0054] In one optional embodiment of this application, the above-mentioned operational amplifier circuit includes:

[0055] An operational amplifier is used to generate a negative voltage signal based on the current difference between the drain current and the source current.

[0056] Specifically, such as Figure 1As shown, operational amplifier U3 receives a voltage signal from the second current sensor U5 at its non-inverting input terminal and a voltage signal from the first current sensor U4 at its inverting input terminal. Through an internal differential amplification mechanism, it directly calculates the difference between the two currents and outputs a voltage proportionally.

[0057] Understandably, when the power switching device is normally turned on or in steady-state conduction, the source current and drain current are basically equal, and the difference is close to zero. The operational amplifier output is close to zero level. At the instant the power switching device is turned off, due to the presence of Miller capacitance inside the device, the drain current decreases later than the source current, causing the drain current to be momentarily greater than the source current, forming a positive current difference. At this time, the operational amplifier outputs a positive voltage signal that is proportional to the difference.

[0058] The scaling circuit is connected between the current acquisition circuit and the operational amplifier to adjust the negative voltage signal output by the operational amplifier.

[0059] Specifically, the scaling circuit consists of multiple precision resistors connected between the current acquisition circuit and the input of the operational amplifier. By setting the resistor ratio, the weak voltage signal (typically in the millivolt range) from the current sensor is converted into an intermediate voltage signal that conforms to the operating range of the operational amplifier, and a linear gain relationship is established between the difference and the output voltage in the process.

[0060] The above settings ensure the system's sensitive recognition of small current differences while avoiding saturation of the algorithm amplifier caused by large current differences.

[0061] A voltage divider circuit, connected to the output of an operational amplifier, is used to scale negative voltage signals.

[0062] Specifically, the voltage divider circuit is connected between the operational amplifier output and the gate drive circuit. It consists of two series resistors, and their connection point serves as the final negative voltage output node. The positive voltage output from the operational amplifier is converted into a negative voltage applied to the IGBT gate through the resistor division relationship. Since the negative power supply used by the drive circuit is negative while the operational amplifier output is positive, the voltage divider circuit, by appropriately selecting the resistor ratio, makes the output node potential negative, and its value increases in negativeness as the operational amplifier output voltage increases.

[0063] In the above embodiments, the operational amplifier is used to sense and generate a control signal corresponding to the current difference, the scaling circuit is used to accurately match the dynamic range of the sensor output and the amplifier input, and the voltage divider circuit is used to convert the control signal into a negative voltage value that can be applied to the gate, so that the negative voltage applied to the gate circuit changes with the physical state of the power switching device.

[0064] In one optional embodiment of this application, the clamping circuit includes:

[0065] The first switching transistor is used to reduce the gate voltage of the power switching device to the reference potential;

[0066] Specifically, such as Figure 1 As shown, the first switching transistor Q4 is connected to the gate of the power switching device, ground, and the output of the comparator. This switching transistor is used to establish a low-impedance path from the gate of the power switching device to ground within nanoseconds after the comparator is triggered to conduct, so as to quickly discharge the gate charge and force the gate voltage to be pulled down to near the ground potential (i.e., the reference potential), thereby eliminating the gate voltage raised by the Miller capacitance through the change of drain-source voltage and realizing Miller clamping.

[0067] The comparator has its inverting input connected to the output of the operational amplifier and its non-inverting input connected to a reference voltage source. The comparator is used to control the on / off state of the first switching transistor.

[0068] Specifically, such as Figure 1 As shown, the high-speed voltage comparator U2 has an inverting input that directly receives the output voltage from the operational amplifier (an analog control signal dynamically generated based on the difference between the drain current and source current of the power switching device, the amplitude of which changes in real time with the operating state of the device). Its non-inverting input is connected to a fixed reference voltage source, which is set to be slightly higher than the minimum negative voltage threshold required for the safe turn-off of the power switching device, and much lower than the upper limit of the gate voltage that may cause false turn-on.

[0069] Understandably, during the power switching device turn-off process, if the current difference gradually increases, the operational amplifier output voltage will rise accordingly. When this voltage exceeds the reference voltage, the comparator will immediately flip to output a high level, triggering the first switch to turn on. Conversely, if the current difference decreases, the operational amplifier output voltage will fall back. When it falls below the reference voltage, the comparator will output a low level, the first switch will turn off, and the normal negative voltage power supply provided by the negative voltage regulation circuit will be restored.

[0070] The above embodiments enable the detection of the operational amplifier output voltage, allowing it to be connected before the Miller effect causes a voltage rise, thus protecting the circuit.

[0071] In one optional embodiment of this application, the voltage divider circuit includes a first resistor and a second resistor, wherein a first end of the first resistor is connected to the output terminal of the operational amplifier, a second end of the first resistor is connected to the first end of the second resistor, a preset negative voltage is applied to the second end of the second resistor, and the connection point of the first resistor and the second resistor is connected to the gate drive circuit.

[0072] Specifically, such as Figure 1As shown, the voltage divider circuit includes a first resistor R3 and a second resistor R4. One end of the first resistor is connected to the output terminal of the operational amplifier. The output of this terminal is a voltage signal obtained by amplifying the difference between the drain current and the source current. The first resistor serves as a resistive path for transmitting this dynamic voltage signal to subsequent circuits, and its resistance value determines the signal attenuation ratio and load capacity. One end of the second resistor is connected to the other end of the first resistor, and the other end is connected to a fixed negative voltage U_, serving as the reference basis for the voltage divider network. The negative voltage at the voltage division point can be adjusted by setting the ratio of the first resistor and the second resistor.

[0073] Furthermore, the voltage divider point (i.e. the connection point between the first resistor and the second resistor) is directly connected to the negative voltage input terminal of the gate drive circuit, serving as the negative voltage source for the switching transistor Q2.

[0074] In one optional embodiment of this application, the operational amplifier circuit further includes a clamping transistor. The cathode of the clamping transistor is connected to the junction of the first resistor and the second resistor, and the anode of the clamping transistor is connected to a preset negative voltage. The clamping transistor is used to limit the negative voltage to the preset voltage when the negative voltage output at the junction exceeds the preset voltage.

[0075] Specifically, the operational amplifier circuit also includes a clamping transistor D3. The first and second resistors form a voltage divider network, converting the control voltage output by the operational amplifier into a negative voltage level suitable for the gate of the power switching device. The connection point of this voltage divider network (i.e., the midpoint between the first and second resistors) is directly connected to the negative voltage input terminal of the gate drive circuit. When the power switching device enters the peak stage of the turn-off process, the drain current decreases rapidly, causing the operational amplifier output voltage to rise rapidly. This pulls the voltage at the voltage divider point to a more negative level, increasing the losses during the turn-off process of the power switching device and even causing circuit overload. This application uses a clamping transistor (cathode connected to the voltage divider node, anode connected to the preset negative voltage, and reverse-parallel connected to the lower end of the voltage divider network). When the voltage at the voltage divider node is lower than the diode's conduction threshold, the diode switches from reverse bias to forward conduction, forming a low-resistance path to adjust the negative voltage to U_.

[0076] In one optional embodiment of this application, the scaling circuit includes a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The third resistor is connected between the non-inverting input of the operational amplifier and a first current sensor. The fourth resistor is connected between the inverting input of the operational amplifier and a second current sensor. The first end of the fifth resistor is connected to the inverting input of the operational amplifier, and the second end of the fifth resistor is grounded. The first end of the sixth resistor is connected between the third resistor and the non-inverting input of the operational amplifier, and the second end of the sixth resistor is connected to the output of the operational amplifier. The third, fourth, fifth, and sixth resistors are used to control the scaling ratio of the operational amplifier.

[0077] Specifically, such as Figure 1 As shown, the third resistor R6 is connected between the non-inverting input of operational amplifier U3 and the first current sensor U4, introducing the voltage signal reflecting the drain current of the power switching device into the positive input of the amplifier proportionally, forming a positive input channel. Similarly, the fourth resistor R7 is connected between the inverting input of operational amplifier U3 and the second current sensor U5, its function being to introduce the voltage signal reflecting the source current into the negative input equivalently, forming a symmetrical acquisition path with the drain current signal. One end of the fifth resistor R8 is connected to the inverting input, and the other end is grounded, establishing a stable DC bias reference point for the inverting input, preventing drift or false triggering caused by floating signal terminals. The first end of the sixth resistor R5 is connected between the third resistor and the non-inverting input of the operational amplifier, and the second end is connected to the output of the operational amplifier, forming a positive feedback path that directly feeds back from the output to the non-inverting input. The ratio of the resistance values ​​of the third, fourth, fifth, and sixth resistors can also determine the scaling ratio of the operational amplifier.

[0078] In one optional embodiment of this application, the gate driving circuit includes:

[0079] The second switching transistor is connected to the control circuit and turns on when it receives a turn-on control signal from the control circuit.

[0080] Specifically, such as Figure 1 As shown, the second switch Q1 turns on when it receives the turn-on command from the control circuit. Its function is to introduce the positive power supply voltage (U+) into the gate of the power switching device to establish a sufficient gate-source voltage to turn it on.

[0081] The third switching transistor is connected to the control circuit and turns on when it receives a turn-off control signal from the control circuit.

[0082] Specifically, such as Figure 1 As shown, the third switch Q2 turns on when it receives a turn-off command. Its function is to guide the negative voltage (U-) to the gate of the power switching device, form a reverse bias, extract gate charge, and accelerate the turn-off process.

[0083] A positive voltage isolation diode is connected between the second switching transistor and the power switching device to prevent positive voltage from being injected into the negative voltage regulation circuit when the second switching transistor is turned on.

[0084] Specifically, such as Figure 1As shown, the positive voltage isolation diode D1 is connected between the second switch Q1 and the gate of the power switching device. Its unidirectional conduction characteristic ensures that when the second switch Q1 is turned on, the positive voltage is transmitted to the gate. When the third switch Q2 is turned on and the negative voltage begins to act, the diode is reverse biased and blocked, preventing the negative voltage from flowing back into the positive voltage power supply path, avoiding the positive voltage power supply from being pulled low or generating a current loop, thereby protecting the stability of the front-end drive power supply.

[0085] A negative voltage isolation diode is connected between the third switching transistor and the power switching device to prevent negative voltage interference when the third switching transistor is turned on.

[0086] Specifically, such as Figure 1 As shown, the negative voltage isolation diode D2 is connected between the third switch Q2 and the gate of the power switching device. Its function is to ensure that the negative voltage is only applied during the turn-off phase and to prevent the positive voltage from flowing into the negative voltage regulation circuit when the second switch Q1 is turned on.

[0087] The seventh resistor is connected between the positive voltage isolation diode and the power switching device to limit the gate charging current of the power switching device.

[0088] Specifically, such as Figure 1 As shown, the seventh resistor R1 is connected in series between the positive voltage isolation diode D1 and the gate of the power switching device, limiting the gate charging current of the power switching device at the moment of turn-on.

[0089] The eighth resistor is connected between the negative voltage isolation diode and the power switching device to limit the discharge rate of the power switching device.

[0090] Similarly, such as Figure 1 As shown, the eighth resistor R2 is connected in series between the negative voltage isolation diode D2 and the gate of the power switching device. Its function is to control the rate of gate charge release when the power switching device is turned off.

[0091] In one specific embodiment, the driving circuit diagram of a power switching device in the prior art is as follows: Figure 2 As shown, it consists of a drive circuit (D1, D2, R1, R2, Q2, Q1), a Miller clamping circuit (Q4), and a control circuit (U1).

[0092] In another specific embodiment, the current flow diagram of this application when the power switching device is turned on is as follows: Figure 3 As shown, the current flow diagram of this application when the power switching device is turned off is as follows: Figure 4As shown, U+ is the positive voltage source, U- is the fixed negative voltage, PGND is the power ground, and DCP is the DC path. It can be understood that when the drive controller U1 does not provide any control signal, the current detected by U4 and U5 is 0. At this time, the output of operational amplifier U3 is 0, and the negative voltage supply to the gate drive circuit is... The initial negative voltage can be adjusted by setting the resistance ratio of R3 and R4. When the power switching device is turned on, the gate drive circuit controls Q1 to turn on, and the current flows in the direction of U+-Q1-D1-R1-Q3-U5-ground. It can be seen that the current i1 detected by U4 is less than the current i2 detected by U5. Therefore, the voltage signal Ui1 output by the current sensor is less than Ui2. This voltage signal is then output by operational amplifier U3 (used for subtraction, with appropriate amplification / scaling ratios set by resistors R5, R6, R7, and R8). This signal is greater than 0. At this time, the negative voltage received by the gate drive current is... In the formula, The signal output by U3 is now closer to the gate voltage. The larger the difference, the closer the negative pressure supply is to the target. When the power switching device is turned off, the gate drive circuit controls Q2 to turn on, and the current flows to ground-U5-R2-D2-Q2-R4-ground. It can be seen that the current i1 detected by U4 is greater than the current i2 detected by U5. Therefore, the voltage signal Ui1 output by the current sensor is greater than Ui2. After passing through the operational amplifier U3, the output signal is less than 0. At this time, the negative voltage received by the gate drive circuit is... Therefore, it can be seen that the negative pressure at this time is closer to The larger the difference, the closer they are. ,when When the value of Uref is greater than the input of comparator U2, Q4 is triggered to turn on, and the gate is pulled low directly. This is Miller clamping.

[0093] Through the above embodiments, the negative pressure changes with the detected current. During startup, a large negative pressure supply is not required, and the negative pressure control circuit outputs a negative pressure further away from the target voltage. However, during shutdown, or when a large spike occurs (when the difference is large), the negative pressure will become closer. In extreme cases, it equals (Restricted by clamping tube) If the spike is too large, it will trigger Miller clamping to prevent circuit damage.

[0094] In one embodiment of this application, a negative pressure control method is provided, such as... Figure 5 As shown, the above negative pressure control method includes:

[0095] Step S201: Obtain the source current of the power switching device and the drain current of the power switching device.

[0096] Specifically, by setting current sensing units in the source and drain circuits of the power switching device respectively, the instantaneous values ​​of the source current and drain current are collected in real time to obtain the aforementioned source current and drain current. It can be understood that at the moment of turn-on, the drain current rises and the source current rises synchronously, and the two are basically equal. In the initial stage of turn-off, the drain current slowly decreases due to the disconnection of the main channel, but the source current decreases first due to the discharge of gate charge, and a difference appears between the two. When the Miller effect occurs, the gate charge is injected in reverse by the Miller capacitance, the drain current still maintains a high value, while the source current has decreased significantly, forming a significant current difference. The relationship between the source current and drain current can reflect the real-time state of the power switching device.

[0097] Step S202: Calculate the difference between the drain current and the source current to obtain the current difference;

[0098] It is understandable that the above current difference is obtained by performing a difference calculation based on the above source current and the above drain current, so as to reflect the dynamic behavior of the power switching device.

[0099] Step S203: Adjust the gate turn-off negative voltage of the power switching device according to the polarity of the current difference.

[0100] Specifically, the negative voltage amplitude applied to the gate is dynamically adjusted according to the polarity and amplitude of the current difference.

[0101] Through the above embodiments, the source current and drain current of the power switching device are used as monitoring objects to observe the operation of the power switching device in real time. Then, the required negative voltage amplitude applied to the gate circuit of the power switching device is determined according to the operation of the power switching device. This realizes the dynamic adjustment of the negative voltage according to the output current of the power switching device, avoiding the negative voltage amplitude being too high, which could increase the power switching device and even damage the circuit. It also avoids the negative voltage amplitude being insufficient to suppress the Miller effect, which could lead to false turn-on.

[0102] To avoid damage to the circuit, in an optional implementation, step S203 includes:

[0103] Step S2031: When the current difference is greater than 0, increase the gate turn-off negative voltage;

[0104] Specifically, if the difference between the drain current and the source current is detected to be greater than zero, it indicates that the power switching device is in the on state, and the current flows in the direction of U+-Q1-D1-R1-Q3-U5-ground. At this time, the operational amplifier outputs a positive voltage, which pulls up the negative voltage, and the negative voltage applied by the gate drive circuit moves closer to the output voltage of the operational amplifier.

[0105] Step S2032: When the current difference is less than 0, reduce the gate turn-off negative voltage.

[0106] Specifically, if the difference between the drain current and the source current is less than zero, it indicates that the power switching device is in the off state, and the current flows from ground to U5 to R2 to D2 to Q2 to R4 to ground. At this time, the operational amplifier outputs a negative voltage, which reduces the negative voltage, and the negative voltage applied by the gate drive circuit moves closer to the fixed negative voltage.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0109] As can be seen from the above description, the embodiments of this application achieve the following technical effects:

[0110] 1) The negative voltage control circuit of this application includes a gate drive circuit, a negative voltage adjustment circuit, a control circuit, and a power switching device. The control circuit outputs a control signal to indicate whether the power switching device is turned off or on. The gate drive circuit, connected between the control circuit and the power switching device, receives the control signal and switches the gate voltage type of the power switching device according to the control signal. The negative voltage adjustment circuit, connected to the gate drive circuit and the power switching device, acquires the output current of the power switching device and adjusts the negative voltage applied to the gate drive circuit according to the output current. This application, through the negative voltage adjustment circuit, adjusts the gate turn-off negative voltage of the power switching device based on the output current of the source and drain of the power switching device, ensuring the immediate response of the power switching device to the control signal. This solves the problem in the prior art where a fixed negative voltage is used to control the power switching device, which easily leads to failure to turn off due to the Miller effect.

[0111] 2) The negative voltage control method of this application uses the source current and drain current of the power switching device as the monitoring objects, observes the operation of the power switching device in real time, and then determines the negative voltage amplitude to be applied to the gate circuit of the power switching device according to the operation of the power switching device. This realizes the dynamic adjustment of the negative voltage according to the output current of the power switching device, avoiding the negative voltage amplitude being too high, which could increase the power switching device and even damage the circuit. It also avoids the negative voltage amplitude being insufficient to suppress the Miller effect, which could lead to false turn-on.

[0112] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A negative pressure control circuit, characterized in that, The negative pressure control circuit includes a gate drive circuit, a negative pressure adjustment circuit, a control circuit, and a power switching device, wherein... The control circuit is used to output a control signal, which is used to indicate whether the power switching device is turned off or on. The gate drive circuit is connected between the control circuit and the power switching device, and is used to receive the control signal and switch the voltage type of the gate voltage of the power switching device according to the control signal; The negative voltage regulation circuit is connected to the gate drive circuit and the power switching device, and is used to collect the output current of the power switching device and adjust the negative voltage applied to the gate drive circuit according to the output current.

2. The negative pressure control circuit according to claim 1, characterized in that, The negative pressure regulating circuit includes: A current acquisition circuit, connected to the power switching device, is used to acquire the output current of the power switching device; An operational amplifier circuit, connected to the current acquisition circuit and the gate drive circuit, is used to adjust the negative voltage applied to the gate drive circuit according to the output current. A clamping circuit, connected to the operational amplifier circuit, is used to reduce the gate voltage of the power switching device to the reference potential when the absolute value of the negative voltage output by the operational amplifier circuit exceeds the reference voltage.

3. The negative pressure control circuit according to claim 2, characterized in that, The current acquisition circuit includes: A first current sensor is connected to the drain of the power switching device and is used to collect the drain current of the power switching device. The second current sensor is connected to the source of the power switching device and is used to collect the source current of the power switching device.

4. The negative pressure control circuit according to claim 3, characterized in that, The operational amplifier circuit includes: An operational amplifier is used to generate a negative voltage signal based on the current difference between the drain current and the source current; A scaling circuit is connected between the current acquisition circuit and the operational amplifier to adjust the negative voltage signal output by the operational amplifier. A voltage divider circuit is connected to the output of the operational amplifier and is used to scale the negative voltage signal.

5. The negative pressure control circuit according to claim 4, characterized in that, The clamping circuit includes: The first switching transistor is used to reduce the gate voltage of the power switching device to the reference potential; The comparator has its inverting input connected to the output of the operational amplifier and its non-inverting input connected to a reference voltage source. The comparator is used to control the on / off state of the first switching transistor.

6. The negative pressure control circuit according to claim 4, characterized in that, The voltage divider circuit includes a first resistor and a second resistor. The first end of the first resistor is connected to the output terminal of the operational amplifier, the second end of the first resistor is connected to the first end of the second resistor, the second end of the second resistor is connected to a preset negative voltage, and the connection point of the first resistor and the second resistor is connected to the gate drive circuit.

7. The negative pressure control circuit according to claim 6, characterized in that, The operational amplifier circuit also includes a clamping transistor. The cathode of the clamping transistor is connected to the connection point of the first resistor and the second resistor, and the anode of the clamping transistor is connected to a preset negative voltage. The clamping transistor is used to limit the negative voltage to the preset voltage when the negative voltage output at the connection point exceeds the preset voltage.

8. The negative pressure control circuit according to claim 4, characterized in that, The scaling circuit includes a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The third resistor is connected between the non-inverting input of the operational amplifier and the first current sensor. The fourth resistor is connected between the inverting input of the operational amplifier and the second current sensor. The first end of the fifth resistor is connected to the inverting input of the operational amplifier, and the second end of the fifth resistor is grounded. The first end of the sixth resistor is connected between the third resistor and the non-inverting input of the operational amplifier, and the second end of the sixth resistor is connected to the output of the operational amplifier. The third, fourth, fifth, and sixth resistors are used to control the scaling ratio of the operational amplifier.

9. The negative pressure control circuit according to claim 4, characterized in that, The gate driving circuit includes: The second switching transistor is connected to the control circuit and turns on when it receives a turn-on control signal from the control circuit. The third switching transistor is connected to the control circuit and turns on when it receives a turn-off control signal from the control circuit. A positive voltage isolation diode is connected between the second switching transistor and the power switching device to prevent positive voltage from being injected into the negative voltage regulation circuit when the second switching transistor is turned on. A negative voltage isolation diode is connected between the third switching transistor and the power switching device to prevent negative voltage interference when the third switching transistor is turned on. The seventh resistor is connected between the positive voltage isolation diode and the power switching device to limit the gate charging current of the power switching device. The eighth resistor is connected between the negative voltage isolation diode and the power switching device to limit the discharge rate of the power switching device.

10. A negative pressure control method, characterized in that, The negative pressure control method is applied to the negative pressure control circuit according to any one of claims 1 to 9, and the negative pressure control method includes: Obtain the source current of the power switching device and obtain the drain current of the power switching device; Calculate the difference between the drain current and the source current to obtain the current difference; The gate turn-off negative voltage of the power switching device is adjusted according to the polarity of the current difference.

11. The negative pressure control method according to claim 10, characterized in that, Adjusting the gate turn-off negative voltage of the power switching device according to the polarity of the current difference includes: When the current difference is greater than 0, the gate turn-off negative voltage is increased; When the current difference is less than 0, the gate turn-off negative voltage is reduced.

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