MOSFET negative feedback active gate drive circuit

Abstract

The application provides a MOSFET / IGBT negative feedback active gate drive circuit, which comprises a low-voltage side drive chip, a turn-on voltage feedback regulation loop, an off voltage feedback regulation loop and a high-voltage side switching speed detection loop; the input ends of the turn-on voltage feedback regulation loop and the off voltage feedback regulation loop are connected with a node E in the switching speed detection loop, and the output ends of the turn-on voltage feedback regulation loop and the off voltage feedback regulation loop are respectively connected with a positive voltage power supply end VCC and a negative voltage power supply end VEE or a ground end GND of the drive chip. The application can effectively inhibit overshoot and oscillation in the switching process of the device, and increase the safety of the device; compared with the traditional gate drive, the method has faster switching speed and smaller loss under the same overshoot; the application realizes self-adaptive adjustment of the switching speed by constructing a feedback circuit, and has faster response.

Description

Technical Field

[0001] This invention relates to the technical field of power electronic drives, specifically to MOSFET negative feedback active gate drive circuits, and more particularly to a MOSFET negative feedback active gate drive circuit with self-adjustable switching speed. Background Technology

[0002] With the rapid development of electric vehicles and power electronics, the demand for high-voltage, high-frequency, and high-speed applications is increasing. As key components in power conversion and control, power devices have a significant impact on the system's performance.

[0003] High switching speeds result in large dv / dt and di / dt, which affect the parasitic capacitance and inductance in the device package and circuit. This can cause overcharging and oscillation during switching, increasing switching losses and EMI, and even posing a risk of device breakdown. Furthermore, the presence of parasitic capacitance means that voltage changes between the drain and source terminals can affect the gate and source terminals, leading to mis-conduction. In bridge arm applications, this can cause crosstalk between the upper and lower transistors, resulting in shoot-through issues.

[0004] To address these issues, researchers have designed different gate drivers. These can be broadly categorized into passive gate drivers and active gate drivers.

[0005] Passive gate drives mainly suppress drain-source voltage oscillations by adding auxiliary passive components. For example, adding an auxiliary capacitor between the gate and source, or adding a gate resistor, can slow down the switching speed of the device, see reference [1]. Although such methods can reduce voltage and current overshoot and oscillation to a certain extent, the addition of auxiliary components will slow down the switching speed of the device and increase losses. Therefore, passive gate drives are not widely used because they cannot effectively suppress oscillations and reduce losses at the same time.

[0006] To better suppress oscillations and crosstalk while minimizing switching losses, active gate driving methods have been proposed. Based on the driving method, these can be categorized into four types: variable gate resistance, variable gate drive voltage, variable gate current, and variable input capacitance. Based on the control strategy, they can be classified into switching control, direct closed-loop control, and model-based indirect control.

[0007] A driving circuit for suppressing spikes and crosstalk in SiC MOSFETs is disclosed in patent document CN114337201A. The driving circuit is connected in the SiC MOSFET driving circuit and includes upper and lower bridge arms. A voltage totem pole structure circuit is connected between the first positive and first negative power supplies of the lower bridge arm. The output terminal of the voltage totem pole structure circuit is connected to the input terminal of the driving resistor circuit and the negative voltage turn-off voltage pull-up circuit. The output terminal of the driving resistor circuit is connected to the input terminal of the current extraction circuit and the current injection circuit. The output terminal of the negative voltage turn-off voltage pull-up circuit is connected to the gate of the SiC MOSFET of the lower bridge arm. The upper bridge arm is symmetrically arranged with the lower bridge arm except that it does not have a negative voltage turn-off voltage pull-up circuit. When the lower MOSFET is turned on, the gate current of the SiC MOSFET is extracted through a current extraction circuit to suppress the turn-on current spike. When the lower MOSFET is turned off, current is injected into the gate of the SiC MOSFET through a current injection circuit to suppress the turn-off voltage spike. After the lower MOSFET is turned off, the drive voltage is pulled up to zero level through a negative voltage turn-off voltage pull-up circuit to suppress the losses caused by crosstalk suppression. Although it can effectively suppress crosstalk and spikes, it requires a complex circuit structure to implement the function, and it cannot achieve adaptive adjustment for different switching rates, making it only suitable for specific operating conditions.

[0008] Patent document CN214125140U discloses a MOSFET gate negative feedback active drive circuit for high-speed driving of wide-bandgap semiconductor devices such as SiC and GaN in bridge arm circuits. Based on the negative feedback control principle, it automatically suppresses gate-source voltage interference without sacrificing switching speed, achieving gate voltage stability under high-speed switching. The circuit includes: a drive push-pull circuit, a drive resistor, an auxiliary capacitor, and an auxiliary MOSFET. The drive push-pull circuit is a common MOSFET driver chip, the drive resistor is a resistor R, the auxiliary capacitor is a capacitor C, and the auxiliary MOSFET is a P-channel MOSFET Qp. By connecting the auxiliary P-channel MOSFET in series with its gate and connecting the source of the auxiliary MOSFET to the gate of the controlled MOSFET, a negative feedback regulation mechanism is constructed. This achieves automatic suppression of gate-source voltage interference without sacrificing switching speed, thus achieving gate voltage stability under high-speed switching. While the method of constructing a feedback loop automatically suppresses gate-source voltage interference, it cannot regulate drain-source voltage and current, and its effect on switching losses and overshoot and oscillation suppression of drain-source voltage and current is limited.

[0009] Therefore, a new technical solution is needed to improve the above-mentioned technical problems. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a MOSFET negative feedback active gate drive circuit.

[0011] According to the present invention, a MOSFET negative feedback active gate driving circuit includes: a driving chip on the low-voltage side, an on-state voltage feedback regulation circuit, an off-state voltage feedback regulation circuit, and a switching speed detection circuit on the high-voltage side; the input terminals of the on-state voltage feedback regulation circuit and the off-state voltage feedback regulation circuit are connected to node E in the switching speed detection circuit, and the output terminals of the on-state voltage feedback regulation circuit and the off-state voltage feedback regulation circuit are respectively connected to the positive voltage power supply terminal VCC and the negative voltage power supply terminal VEE or the ground terminal GND of the driving chip.

[0012] Preferably, the switching speed detection circuit includes a capacitor C. E and a voltage divider resistor R E The capacitor C E and voltage divider resistor R E Series connection, capacitor C E One end is connected to the drain of the controlled MOSFET in the high-voltage circuit, and the other end is connected to the voltage divider resistor R. E Connected, voltage divider resistor R E The other end is connected to the source of the controlled MOSFET.

[0013] Preferably, the capacitor C E The voltage V between the drain and source of the controlled MOSFET ds The rate of change is converted into current, which is then applied to the voltage divider resistor R. E A voltage drop is generated, which is used to detect the switching rate; the final output is the capacitance C. E With voltage divider resistor R E Voltage V at connection point E E The expression for the voltage at point E is: .

[0014] Preferably, the turn-on voltage feedback regulation circuit is a negative feedback circuit composed of a high-speed operational amplifier as its core component, including a positive input resistor R0, a negative input resistor R1, a feedback resistor R2, and a feedback capacitor C1; one end of the positive input resistor R0 is connected to the bias voltage V. B1 One end of the inverting input resistor R1 is connected to the inverting input of the high-speed operational amplifier, and the other end is connected to point E in the detection circuit. One end of the feedback resistor R2 is connected to the inverting input of the operational amplifier, and the other end is connected to the output of the operational amplifier. The feedback capacitor C1 is connected in parallel across the feedback resistor R2. The output of the high-speed operational amplifier is connected to the gate of the auxiliary MOSFET, and the turn-on voltage feedback adjustment circuit adjusts the gate voltage of the auxiliary MOSFET through feedback.

[0015] Preferably, the turn-on auxiliary MOSFET is a P-channel MOSFET, with its power supply terminal connected to its source and its drain connected to the positive voltage power supply terminal VCC of the driver chip; a capacitor C3 is connected between the drain of the turn-on auxiliary MOSFET and the ground terminal GND of the circuit. The output voltage of the high-speed operational amplifier conforms to the following expression:

[0016] By adjusting the bias voltage V B1 The output characteristics of the op-amp are adjusted by the ratio of R2 to R1.

[0017] Preferably, the bias voltage V B1 It is supplied by an external power source or generated by a voltage divider circuit on the circuit board. The voltage value is adjusted according to the actual situation, and the voltage range is 0-5V.

[0018] Preferably, the turn-off voltage feedback regulation circuit includes a forward input resistor R3, a reverse input resistor R4, a feedback resistor R5, and a feedback capacitor C2. One end of the forward input resistor R3 is connected to the bias voltage V. B2 One end of the inverting input resistor R4 is connected to the inverting input of the high-speed operational amplifier, and the other end is connected to point E in the detection circuit. One end of the feedback resistor R5 is connected to the inverting input of the operational amplifier, and the other end is connected to the output of the operational amplifier. The feedback capacitor C2 is connected in parallel across the feedback resistor R5 to filter the feedback signal. The output of the high-speed operational amplifier is connected to the gate of the turn-off auxiliary MOSFET, and the turn-off voltage feedback adjustment circuit adjusts the gate voltage of the auxiliary MOSFET through feedback.

[0019] Preferably, the shutdown auxiliary MOSFET is an N-channel MOSFET, with a negative voltage source connected to its source (S) and its drain (D) connected to the negative voltage supply terminal VEE of the driver chip to provide the negative voltage for driving. A capacitor C4 is connected between the drain of the shutdown auxiliary MOSFET and the ground terminal GND of the circuit.

[0020] Preferably, the bias voltage V B2 It is supplied by an external power source or generated by a voltage divider circuit on the circuit board. The voltage value is adjusted according to the actual situation, and the voltage range is 0-5V.

[0021] Preferably, the driving chip is a common driving chip, with its output terminal connected to the controlled MOSFET, and a gate resistor Rg added in between according to the actual situation.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention can effectively suppress overshoot and oscillation during device switching, increasing device safety; compared with traditional gate drive, under the same overshoot, this method has faster switching speed and lower losses. 2. This invention achieves adaptive adjustment of switching speed by constructing a feedback circuit, resulting in a faster response; 3. In the turn-on and turn-off circuit, the present invention uses MOSFET as a control device to achieve stepless control, so that the controlled device (MOSFET) works under the best operating conditions. 4. The circuit structure and control method of the present invention are simple and easy to implement, have high stability, and have low circuit construction costs. Attached Figure Description

[0023] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is an overall structural diagram of the gate driving circuit of the present invention; Figure 2 This is a circuit diagram of the switching rate detection loop of the present invention; Figure 3 This is a circuit diagram of the turn-on voltage feedback regulation loop of the present invention; Figure 4 This is a circuit diagram of the turn-off voltage feedback regulation loop of the present invention; Figure 5 This is a waveform diagram of the opening process of the present invention; Figure 6 This is a waveform diagram of the shutdown process of the present invention. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0025] Example 1: According to the present invention, a MOSFET negative feedback active gate driving circuit includes: a driving chip on the low-voltage side, an on-state voltage feedback regulation circuit, an off-state voltage feedback regulation circuit, and a switching speed detection circuit on the high-voltage side; the input terminals of the on-state voltage feedback regulation circuit and the off-state voltage feedback regulation circuit are connected to node E in the switching speed detection circuit, and the output terminals of the on-state voltage feedback regulation circuit and the off-state voltage feedback regulation circuit are respectively connected to the positive voltage power supply terminal VCC and the negative voltage power supply terminal VEE or the ground terminal GND of the driving chip.

[0026] The switching speed detection circuit includes a capacitor C. E and a voltage divider resistor R E The capacitor C E and voltage divider resistor R E Series connection, capacitor C E One end is connected to the drain of the controlled MOSFET in the high-voltage circuit, and the other end is connected to the voltage divider resistor R. E Connected, voltage divider resistor R E The other end is connected to the source of the controlled MOSFET.

[0027] Capacitor C E The voltage V between the drain and source of the controlled MOSFET ds The rate of change is converted into current, which is then applied to the voltage divider resistor R. E A voltage drop is generated, which is used to detect the switching rate; the final output is the capacitance C. E With voltage divider resistor R E Voltage V at connection point E E The expression for the voltage at point E is: .

[0028] The open-circuit voltage feedback regulation loop is a negative feedback loop composed of a high-speed operational amplifier as its core component, including a positive input resistor R0, a negative input resistor R1, a feedback resistor R2, and a feedback capacitor C1; one end of the positive input resistor R0 is connected to the bias voltage V. B1 One end of the inverting input resistor R1 is connected to the inverting input of the high-speed operational amplifier, and the other end is connected to point E in the detection circuit. One end of the feedback resistor R2 is connected to the inverting input of the operational amplifier, and the other end is connected to the output of the operational amplifier. The feedback capacitor C1 is connected in parallel across the feedback resistor R2. The output of the high-speed operational amplifier is connected to the gate of the auxiliary MOSFET, and the turn-on voltage feedback adjustment circuit adjusts the gate voltage of the auxiliary MOSFET through feedback.

[0029] The turn-on auxiliary MOSFET is a P-channel MOSFET, with its power supply terminal connected to its source and its drain connected to the positive voltage supply terminal VCC of the driver chip; a capacitor C3 is connected between the drain of the turn-on auxiliary MOSFET and the ground terminal GND of the circuit. The output voltage of the high-speed operational amplifier conforms to the following expression:

[0030] By adjusting the bias voltage V B1 The output characteristics of the op-amp are adjusted by the ratio of R2 to R1.

[0031] Bias voltage VB1 It is supplied by an external power source or generated by a voltage divider circuit on the circuit board. The voltage value is adjusted according to the actual situation, and the voltage range is 0-5V.

[0032] The turn-off voltage feedback regulation circuit includes a forward input resistor R3, a reverse input resistor R4, a feedback resistor R5, and a feedback capacitor C2. One end of the forward input resistor R3 is connected to the bias voltage V. B2 One end of the inverting input resistor R4 is connected to the inverting input of the high-speed operational amplifier, and the other end is connected to point E in the detection circuit. One end of the feedback resistor R5 is connected to the inverting input of the operational amplifier, and the other end is connected to the output of the operational amplifier. The feedback capacitor C2 is connected in parallel across the feedback resistor R5 to filter the feedback signal. The output of the high-speed operational amplifier is connected to the gate of the turn-off auxiliary MOSFET, and the turn-off voltage feedback adjustment circuit adjusts the gate voltage of the auxiliary MOSFET through feedback.

[0033] The shutdown auxiliary MOSFET is an N-channel MOSFET with a negative voltage source connected to its source (S) and its drain (D) connected to the negative voltage supply terminal VEE of the driver chip to provide the negative voltage for driving. A capacitor C4 is connected between the drain of the shutdown auxiliary MOSFET and the ground terminal GND of the circuit.

[0034] Bias voltage V B2 It is supplied by an external power source or generated by a voltage divider circuit on the circuit board. The voltage value is adjusted according to the actual situation, and the voltage range is 0-5V.

[0035] The driver chip is a common driver chip, and the output terminal is connected to the controlled MOSFET. A gate resistor Rg is added in the middle according to the actual situation.

[0036] Example 2: This invention effectively suppresses oscillations and overshoot during device switching without significantly increasing device switching losses; it achieves active gate drive arrangement through simple and low-cost circuit design; it constructs a negative feedback loop to achieve autonomous adjustment of turn-on and turn-off speeds; and it can adapt to different driving conditions by changing the gain of the feedback operational amplifier.

[0037] The purpose of this invention is to provide a MOSFET negative feedback active gate drive circuit with adjustable switching speed, which effectively suppresses overshoot and oscillation generated during device switching, while solving the problem of increased losses caused by traditional drives when suppressing oscillation.

[0038] The present invention relates to a drive circuit that connects a drive signal to a controlled MOSFET. A MOSFET has three pins: gate (G), drain (D), and source (S); an IGBT has three pins: gate (G), collector (C), and emitter (E).

[0039] This design consists of a low-voltage side driver chip, an on-state voltage feedback regulation circuit, an off-state voltage feedback regulation circuit, and a high-voltage side switching speed detection circuit. For example... Figure 1 The input terminals of the open and close voltage feedback regulation circuits are connected to node E in the switching speed detection circuit, while the outputs are connected to the positive voltage power supply terminal VCC and the negative voltage power supply terminal VEE (or GND) of the driver chip, respectively.

[0040] like Figure 2 The switching speed detection circuit consists of a small capacitor CE and a voltage divider resistor RE connected in series. One end of the capacitor is connected to the drain (D) of the controlled MOSFET in the high-voltage circuit, and the other end is connected to the voltage divider resistor. The other end of the resistor is connected to the source (S) of the controlled MOSFET. The capacitor converts the rate of change of the voltage Vds between the MOSFET's drain and source into current, generating a voltage drop across the resistor, thereby detecting the switching speed. The final output is the voltage VE at the point E where the capacitor and resistor are connected. The expression for the voltage at point E is:

[0041] like Figure 3 The turn-on voltage feedback regulation loop is a negative feedback loop composed of a high-speed operational amplifier as its core component. Its main components are: a positive input resistor R0, one end of which is connected to the bias voltage VB1, and the other end to the positive input terminal of the high-speed operational amplifier. The bias voltage can be supplied by an external power supply or generated by a voltage divider circuit on the circuit board, and its value is adjusted according to the actual situation, typically 0-5V; an inverting input resistor R1, one end of which is connected to the inverting input terminal of the high-speed operational amplifier, and the other end to point E in the detection circuit; a feedback resistor R2, one end of which is connected to the inverting input terminal of the operational amplifier, and the other end to the output of the operational amplifier; a feedback capacitor C1 connected in parallel across the feedback resistor R2 to filter the feedback signal and improve the stability of the feedback loop; finally, the output terminal of the high-speed operational amplifier is connected to the gate (G) of the turn-on auxiliary MOSFET. The turn-on voltage feedback regulation loop adjusts the gate (G) voltage of the auxiliary MOSFET through feedback. The turn-on auxiliary MOSFET is a P-channel MOSFET. Its power supply terminal is connected to its source (S), and its drain (D) is connected to the positive voltage supply terminal VCC of the driver chip to provide the positive voltage for driving. In order to ensure the response speed of the power supply voltage, a small capacitor C3 must be connected between the drain of the turn-on auxiliary MOSFET and the ground (GND) of the circuit.

[0042] The output voltage of the op-amp conforms to the following expression:

[0043] The output characteristics of the operational amplifier can be adjusted by adjusting the bias voltage VB1 and the ratio of R2 to R1, thereby adapting to different operating conditions.

[0044] like Figure 4 The turn-off voltage feedback regulation loop design is similar to the turn-on loop. Its main components include: a positive input resistor R3, one end of which is connected to the bias voltage VB2, and the other end to the positive input terminal of the high-speed operational amplifier. The bias voltage can be supplied by an external power supply or generated by a voltage divider circuit on the circuit board, and its value is adjusted according to the actual situation, typically 0-5V; an inverting input resistor R4, one end of which is connected to the inverting input terminal of the high-speed operational amplifier, and the other end to point E in the detection loop; a feedback resistor R5, one end of which is connected to the inverting input terminal of the operational amplifier, and the other end to the output of the operational amplifier; a feedback capacitor C2 connected in parallel across the feedback resistor R5 to filter the feedback signal and improve the stability of the feedback loop; finally, the output terminal of the high-speed operational amplifier is connected to the gate (G) of the turn-off auxiliary MOSFET. The turn-off voltage feedback regulation loop adjusts the gate voltage of the auxiliary MOSFET through feedback. The turn-off auxiliary MOSFET is an N-channel MOSFET, with a negative voltage source connected to its source (S) terminal, and its drain (D) terminal connected to the negative voltage supply terminal VEE of the driver chip to provide the driving negative voltage. To ensure the response speed of the power supply voltage, a small capacitor C4 must be connected between the drain of the auxiliary MOSFET and the ground (GND) of the circuit.

[0045] A standard driver chip can be used. The output terminal is connected to the controlled MOSFET, and a gate resistor Rg can be added in the middle according to the actual situation.

[0046] The circuit structure of this invention is designed for driving MOSFETs, but the principle is also applicable to driving wide bandgap semiconductor devices such as GaN. The positive and negative input terminals of the high-speed operational amplifier can be replaced by a pre-set voltage source to supply the original feedback signal, thereby realizing the control of the active switching speed. In addition to being applicable to overshoot, oscillation suppression, and loss reduction, the circuit design scheme is also applicable to EMI suppression and crosstalk in the bridge arm.

[0047] This invention employs a design that uses an auxiliary MOSFET to regulate the power supply voltage of the driver chip; designs an on-state voltage feedback regulation circuit, a off-state voltage feedback regulation circuit, and a high-voltage side switching speed detection circuit; adds a small capacitor between the power supply terminal of the driver chip and ground (GND) to maintain the voltage regulation response speed; and designs the overall topology of the negative feedback active gate drive circuit.

[0048] like Figures 1 to 4 As shown, this design scheme comprises three main components: an on-state voltage feedback regulation circuit, a off-state voltage feedback regulation circuit, and a high-voltage side switching speed detection circuit. The implementation method and principle of the design scheme will be explained below based on the specific switching process.

[0049] like Figure 1 As shown, during the turn-on process, the PWM signal received at the signal input terminal of the driver chip changes from low to high, and the driver chip outputs a high level (i.e., VCC), which charges the gate of the MOSFET in the power circuit through the gate resistor Rg. The waveform of the MOSFET turn-on process is as follows: Figure 5 As shown, the solid line represents the ideal waveform of the MOSFET turn-on process after incorporating this design, while the dashed line represents the MOSFET turn-on waveform under traditional gate drive. In the first and second stages of the turn-on process, before Vgs rises from the negative voltage VEE and reaches the Miller plateau voltage, the turn-on voltage feedback regulation loop is almost ineffective because Vds remains unchanged. This stage has little impact on the overshoot oscillation of the turn-on process current; therefore, the turn-on speed should be accelerated as much as possible to reduce switching losses and thermal effects. In the third stage, when Vgs reaches the Miller plateau, i.e., when Ids reaches the load current, Vds begins to decrease. At the beginning of this stage, Ids is prone to overshoot and oscillation, and the turn-on voltage feedback regulation loop begins to function. The specific working principle is as follows: Figure 2 As shown, the sensing capacitor CE is connected in series with the resistor RE and then in parallel to the drain and source terminals of the MOSFET. When the Vds voltage starts to drop, due to the characteristics of the capacitor, the capacitor CE begins to discharge, and the resulting discharge current generates a voltage drop across the resistor RE. The potential expression at point E is:

[0050]

[0051] Point E is connected to the negative input of the operational amplifier in the turn-on voltage feedback regulation circuit for feedback regulation, such as... Figure 3 As shown.

[0052] The turn-on voltage feedback regulation loop is a negative feedback loop with a high-speed operational amplifier as its core component. Its main components are: a positive input resistor R0, one end of which is connected to the bias voltage VB1, and the other end to the positive input terminal of the high-speed operational amplifier. The bias voltage can be supplied by an external power supply or generated by a voltage divider circuit on the circuit board, and its value is adjusted according to the actual situation, typically 0-5V; an inverting input resistor R1, one end of which is connected to the inverting input terminal of the high-speed operational amplifier, and the other end to point E in the detection circuit; a feedback resistor R2, one end of which is connected to the inverting input terminal of the operational amplifier, and the other end to the output of the operational amplifier; a feedback capacitor C1 connected in parallel across the feedback resistor R2 to filter the feedback signal and improve the stability of the feedback loop; finally, the output terminal of the high-speed operational amplifier is connected to the gate (G) of the turn-on auxiliary MOSFET. The turn-on voltage feedback regulation loop adjusts the gate voltage of the auxiliary MOSFET through feedback. The turn-on auxiliary MOSFET is a P-channel MOSFET, with its power supply terminal connected to its source (S) terminal, and its drain (D) terminal connected to the positive voltage supply terminal VCC of the driver chip to provide the positive driving voltage. To ensure the response speed of the power supply voltage, a small capacitor C3 must be connected between the drain of the auxiliary MOSFET and the ground (GND) of the circuit.

[0053] The output voltage of the op-amp conforms to the following expression:

[0054] Therefore, we can adjust the output characteristics of the op-amp by adjusting the bias voltage VB1 and the ratio of R2 to R1, so as to adapt to different operating conditions.

[0055] It can be known that when The larger the value of Ids, i.e., the faster the rate of change of voltage and current, the more severe the overshoot and oscillation, and the greater the damage to the device. Since the turn-on process Vds decreases, VE is a negative voltage. Therefore, from the above formula, it can be seen that when... When the negative pressure is greater, The larger the absolute value, the higher the output voltage of the op-amp. The larger. For example... Figure 3 op-amp output It is connected to the gate of the turn-on auxiliary MOSFET Q2, therefore The larger the gate voltage (Vgs), the higher the gate voltage of Q2. Since it's a P-type MOSFET, its source voltage (S) remains constant at the system supply voltage (+16V). Therefore, the higher the gate voltage, the smaller the absolute value of Vgs (which is negative). Because the auxiliary MOSFET operates in the saturation region, it can be considered an adjustable constant current source. The smaller the absolute value of Vgs, the smaller the saturation current through its channel according to the MOSFET's characteristic curve. This means the smaller the current flowing into VCC to the gate of the controlled MOSFET, slowing down the charging rate of its input capacitor Ciss and reducing the MOSFET's switching speed, thus suppressing the rate of change of Vds. Similarly, when... The smaller the value, the lower the op-amp output voltage. The smaller the value of the gate voltage Vgs, the larger the absolute value of the gate voltage Vgs that turns on the auxiliary MOSFET. This results in a larger current flowing from VCC to the gate of the controlled MOSFET, accelerating the charging rate of its input capacitor Ciss, and thus increasing the rate of change of Vds, forming negative feedback. In the final stage of the turn-on process, from the rise of Vgs from the Miller plateau voltage to the supply voltage VCC, since both Vds and Ids are constant during this stage, the switching rate does not affect the overshoot and oscillation characteristics of the voltage and current. Therefore, the negative feedback loop does not function in this stage, does not suppress the charging current of Ciss, and maximizes the turn-on speed.

[0056] The negative feedback regulation principle during the turn-off process is basically the same as that during the turn-on process. The PWM signal received at the signal input terminal of the driver chip changes from high to low, and the driver chip outputs a negative voltage (VEE). The gate of the controlled MOSFET discharges through the gate resistor Rg, thus achieving turn-off. The waveform of the MOSFET turn-off process is as follows: Figure 6 As shown, the solid line represents the ideal waveform of the MOSFET turn-off process after incorporating this design, while the dashed line represents the MOSFET turn-off waveform under traditional gate drive. In the first stage of the turn-off process, i.e., as Vgs decreases from VCC to the Miller plateau voltage, since both voltage Vds and current Ids remain constant, the negative feedback regulation loop does not function and does not suppress the switching rate, resulting in a faster switching rate and lower switching losses. In the second stage, the Miller plateau stage, Vds voltage begins to rise until it reaches the bus voltage. In this stage, the negative feedback regulation loop begins to function, and its principle is similar to the turn-on process. Point E is connected to the negative input of the op-amp in the turn-on voltage feedback regulation loop for feedback regulation, as shown below. Figure 4 As shown.

[0057] The turn-off voltage feedback regulation loop design is similar to the turn-on loop. Its main components are: a positive input resistor R3, one end of which is connected to the bias voltage VB2, and the other end to the positive input terminal of the high-speed operational amplifier. The bias voltage can be supplied by an external power supply or generated by a voltage divider circuit on the circuit board, and its value is adjusted according to the actual situation, typically 0-5V; an inverting input resistor R4, one end of which is connected to the inverting input terminal of the high-speed operational amplifier, and the other end to point E in the detection loop; a feedback resistor R5, one end of which is connected to the inverting input terminal of the operational amplifier, and the other end to the output of the operational amplifier; a feedback capacitor C2 connected in parallel across the feedback resistor R5 to filter the feedback signal and improve the stability of the feedback loop; finally, the output terminal of the high-speed operational amplifier is connected to the gate (G) of the turn-off auxiliary MOSFET. The turn-off voltage feedback regulation loop adjusts the gate voltage of the auxiliary MOSFET through feedback. The turn-off auxiliary MOSFET is an N-channel MOSFET, with a negative voltage source connected to its source (S) terminal, and its drain (D) terminal connected to the negative voltage supply terminal VEE of the driver chip to provide the driving negative voltage. To ensure the response speed of the power supply voltage, a small capacitor C4 (usually around 5nF) must be connected between the drain of the auxiliary MOSFET and the ground (GND) of the circuit.

[0058] The output voltage of the op-amp conforms to the following expression:

[0059] We can adjust the output characteristics of the op-amp by adjusting the bias voltage VB2 and the ratio of R5 to R4, thereby adapting to different operating conditions.

[0060] when The larger the value, meaning the faster the rate of change of voltage and current, the more severe the overshoot and oscillation of voltage during the turn-off process, and the greater the damage to the device. From the above formula, it can be seen that when... When it is larger, The larger the value, the higher the output voltage of the op-amp. The smaller. For example... Figure 4 op-amp output The gate of the turn-on auxiliary MOSFET Q3 is connected. Q3 is an N-type MOSFET, and its source (S) is connected to the negative voltage (-2V) of the power supply. The larger the gate voltage Vgs, the smaller the discharge current flowing through MOSFET Q3, thus forming negative feedback to suppress the switching speed. In the third and fourth stages, when the current decreases and Vgs reaches the negative voltage VEE, the switching rate has little impact on the overshoot oscillation. Therefore, the negative feedback regulation is ineffective in this stage, resulting in a faster switching rate and lower switching losses.

[0061] Those skilled in the art can understand this embodiment as a more specific description of Embodiment 1.

[0062] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0063] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A MOSFET negative feedback active gate drive circuit, characterized in that, include: The system includes a low-voltage side drive chip, an on-state voltage feedback regulation circuit, an off-state voltage feedback regulation circuit, and a high-voltage side switching speed detection circuit. The input terminals of the on-state voltage feedback regulation circuit and the off-state voltage feedback regulation circuit are connected to node E in the switching speed detection circuit. The output terminals of the on-state voltage feedback regulation circuit and the off-state voltage feedback regulation circuit are connected to the positive voltage power supply terminal VCC and the negative voltage power supply terminal VEE or the ground terminal GND of the drive chip, respectively. The turn-on voltage feedback regulation circuit is a negative feedback circuit composed of a high-speed operational amplifier as its core component, including a positive input resistor R0, a negative input resistor R1, a feedback resistor R2, and a feedback capacitor C1; one end of the positive input resistor R0 is connected to the bias voltage V. B1 One end of the inverting input resistor R1 is connected to the inverting input of the high-speed operational amplifier, and the other end is connected to point E in the detection circuit. One end of the feedback resistor R2 is connected to the inverting input of the operational amplifier, and the other end is connected to the output of the operational amplifier. The feedback capacitor C1 is connected in parallel across the feedback resistor R2. The output of the high-speed operational amplifier is connected to the gate of the turn-on auxiliary MOSFET, and the turn-on voltage feedback adjustment circuit adjusts the gate voltage of the auxiliary MOSFET through feedback. The turn-on auxiliary MOSFET is a P-channel MOSFET, with its power supply terminal connected to its source and its drain connected to the positive voltage power supply terminal VCC of the driver chip; a capacitor C3 is connected between the drain of the turn-on auxiliary MOSFET and the ground terminal GND of the circuit. The output voltage of the high-speed operational amplifier conforms to the following expression: By adjusting the bias voltage V B1 The output characteristics of the op-amp are adjusted by the ratio of R2 to R1; The turn-off voltage feedback regulation circuit includes a forward input resistor R3, a reverse input resistor R4, a feedback resistor R5, and a feedback capacitor C2. One end of the forward input resistor R3 is connected to the bias voltage V. B2 One end of the inverting input resistor R4 is connected to the inverting input of the high-speed operational amplifier, and the other end is connected to point E in the detection circuit. One end of the feedback resistor R5 is connected to the inverting input of the operational amplifier, and the other end is connected to the output of the operational amplifier. The feedback capacitor C2 is connected in parallel across the feedback resistor R5 to filter the feedback signal. The output of the high-speed operational amplifier is connected to the gate of the turn-off auxiliary MOSFET, and the turn-off voltage feedback adjustment circuit adjusts the gate voltage of the auxiliary MOSFET through feedback. The shutdown auxiliary MOSFET is an N-channel MOSFET with a negative voltage source connected to its source (S) and its drain (D) connected to the negative voltage supply terminal VEE of the driver chip to provide the negative voltage for driving. A capacitor C4 is connected between the drain of the shutdown auxiliary MOSFET and the ground terminal GND of the circuit.

2. The MOSFET negative feedback active gate drive circuit according to claim 1, characterized in that, The switching speed detection circuit includes a capacitor C. E and a voltage divider resistor R E The capacitor C E and voltage divider resistor R E Series connection, capacitor C E One end is connected to the drain of the controlled MOSFET in the high-voltage circuit, and the other end is connected to the voltage divider resistor R. E Connected, voltage divider resistor R E The other end is connected to the source of the controlled MOSFET.

3. The MOSFET negative feedback active gate drive circuit according to claim 2, characterized in that, The capacitor C E The voltage V between the drain and source of the controlled MOSFET ds The rate of change is converted into current, which is then applied to the voltage divider resistor R. E A voltage drop is generated, which is used to detect the switching rate; the final output is the capacitance C. E With voltage divider resistor R E Voltage V at connection point E E The expression for the voltage at point E is: 。 4. The MOSFET negative feedback active gate drive circuit according to claim 1, characterized in that, The bias voltage V B1 It is supplied by an external power source or generated by a voltage divider circuit on the circuit board. The voltage value is adjusted according to the actual situation, and the voltage range is 0-5V.

5. The MOSFET negative feedback active gate drive circuit according to claim 1, characterized in that, The bias voltage V B2 It is supplied by an external power source or generated by a voltage divider circuit on the circuit board. The voltage value is adjusted according to the actual situation, and the voltage range is 0-5V.

6. The MOSFET negative feedback active gate drive circuit according to claim 1, characterized in that, The driving chip is a common driving chip, with its output terminal connected to the controlled MOSFET, and a gate resistor Rg added in the middle according to the actual situation.

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