Control method for improving field effect transistor turn-on current and control circuit thereof

Abstract

The invention particularly relates to a control method for improving the turn-on current of a field effect transistor. The control method comprises the following steps: connecting a first VCC end with an OUT end through a field effect transistor Q1; the collector electrode of the triode Q2 is connected with the grid electrode of the field effect transistor Q1 to form a control path; a control signal of a control end is applied to the base electrode of the triode Q2 so as to adjust the conduction state of the field effect transistor Q1; and the current path of the grid electrode of the field effect transistor Q1 is controlled through the conduction and cut-off of the triode Q2. Meanwhile, the invention further discloses a control circuit applying the method. According to the method and the circuit, the conduction and turn-off processes of the field effect transistor Q1 are accurately controlled, so that the current impact is reduced, the loss in the circuit is reduced, the service life of the field effect transistor is prolonged, and the turn-on current characteristic is improved.

Description

Technical Field

[0001] The present invention specifically relates to a control method for improving turn-on current and a control circuit for this method. Background Art

[0002] In modern power electronic systems, the field-effect transistor (MOSFET) is widely used in switching power supplies, motor drives, power amplifiers, etc. due to its advantages such as high switching speed, low on-resistance, and high input impedance. However, in the actual application of the field-effect transistor, the problem of current overshoot generated during the turn-on instant has always been a key factor restricting circuit performance and device reliability. When the field-effect transistor switches from the off state to the on state, due to the rapid charging of the gate capacitance, the drain current will rise rapidly, generating a large current impact. This transient current will not only increase the switching loss of the circuit, but may also cause electrical stress concentration, accelerate the aging of the field-effect transistor, and even lead to device failure.

[0003] In the prior art, for the problem of excessive turn-on current of the field-effect transistor, the common solutions include the following several kinds.

[0004] (1) Gate drive resistance adjustment method: By connecting a resistor in series with the gate to slow down the rising rate of the gate voltage, thereby reducing the change rate of the drain current. However, a resistor with a fixed resistance value is difficult to adapt to the dynamic requirements under different working conditions, and an excessive resistor will cause a decrease in switching speed and affect system efficiency (see Chinese Patent Application No.: CN201510123456.7).

[0005] (2) Active gate drive circuit: Using a dedicated drive chip or complex control logic to achieve slope control of the gate voltage. Although such a scheme can accurately adjust the turn-on speed, it increases the circuit complexity and cost, and is sensitive to high-frequency noise (Comparative Document US2017 / 0256321A1).

[0006] (3) Parallel buffer circuit: Connecting an RC absorption network or a diode-capacitor combination in parallel between the drain and source to suppress current spikes. However, such a method will introduce additional power consumption and volume, and has limited effects on high-frequency switching scenarios (Reference: "Power Semiconductor Devices and Applications", 2020 Edition).

[0007] The main defects of the above prior art include the following.

[0008] I. Lack of flexibility: The traditional gate resistance adjustment method cannot dynamically adapt to load changes or fluctuations in the working environment, resulting in limited optimization effects. II. High cost and complexity: The active drive scheme relies on dedicated chips or complex control algorithms, increasing the design difficulty and manufacturing cost. III. Conflict between efficiency and reliability: Although the buffer circuit can suppress current surges, it sacrifices system efficiency and compactness, especially in high-temperature or high-density packaging scenarios. IV. Weak anti-interference ability: Existing schemes are sensitive to power supply noise and parasitic parameters, easily causing distortion of control signals and affecting the stable switching of field effect transistors. Summary of the Invention

[0009] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, an object of the present invention is to propose a control method for improving the turn-on current and a control circuit for this method, which can reduce current surges, reduce losses in the circuit, improve the service life of field effect transistors and improve the turn-on current characteristics, and also have good anti-interference ability and stability, can work reliably in different working environments, have high stability and meet different application requirements, and have the advantages of flexible control.

[0010] The present invention discloses a control method for improving the turn-on current of a field effect transistor, including the following steps.

[0011] Connect the first VCC terminal to the OUT terminal through the field effect transistor Q1.

[0012] Form a control path by connecting the collector of the triode Q2 to the gate of the field effect transistor Q1.

[0013] Apply the control signal of the control terminal to the base of the triode Q2 to adjust the conduction state of the field effect transistor Q1.

[0014] Control the current path of the gate of the field effect transistor Q1 through the conduction and cut-off of the triode Q2.

[0015] Specifically further, a third resistor R3 is provided between the base of the triode Q2 and the control terminal to limit the drive current input to the base of the triode Q2.

[0016] Specifically further, a fourth resistor R4 is connected in parallel between the base and the emitter of the triode Q2 to provide a path for discharging the base bias current of the triode Q2.

[0017] Specifically further, the gate drive impedance of the field effect transistor Q1 is adjusted by connecting the second resistor R2 between the base of the field effect transistor Q1 and the collector of the triode Q2.

[0018] Specifically further, a second capacitor C2 is provided between the first VCC terminal and the ground for power supply filtering, and a third capacitor C3 is provided between the OUT terminal and the ground for output terminal filtering.

[0019] Specifically further, the conduction degree of the triode Q2 is controlled by adjusting the signal level of the control terminal, and further, the gate charging rate of the field effect transistor Q1 is controlled.

[0020] Specifically further, when a high level is applied to the control terminal, the triode Q2 conducts and pulls down the base potential of the field effect transistor Q1, accelerating the turn-off process of the field effect transistor Q1.

[0021] Specifically further, when a low level is applied to the control terminal, the triode Q2 is cut off, and a conduction current is provided to the gate of the field effect transistor Q1 through an external circuit.

[0022] Meanwhile, the present invention also provides a control circuit applying the above control method for improving the turn-on current of a field effect transistor, including a first VCC terminal and an OUT terminal. The VCC terminal and the OUT terminal are connected through a field effect transistor Q1, and further includes a triode Q2. The base of the field effect transistor Q1 is connected to the collector of the triode Q2, and the base of the triode Q2 is connected with a control terminal.

[0023] Specifically further, a third resistor R3 is provided between the base of the triode Q2 and the control terminal. A fourth resistor R4 is connected between the base and the emitter of the triode Q2. The gate of the field effect transistor Q1 is connected to the collector of the triode Q2 through a second resistor R2. One end of the first VCC terminal is connected to one end of a second capacitor C2, one end of the second capacitor C2 is connected to a ground terminal GND, one end of the OUT terminal is connected to one end of a third capacitor C3, and the other end of the third capacitor C3 is connected to the ground terminal GND.

[0024] The beneficial effects of the present invention are as follows.

[0025] First, by precisely controlling the turn-on and turn-off processes of the field effect transistor Q1, the present circuit reduces current impact, lowers the loss in the circuit, improves the service life of the field effect transistor, and improves the turn-on current characteristics.

[0026] Second, a first resistor R1 and a first capacitor C1 are reasonably arranged on the field effect transistor Q1, enabling the circuit to have good anti-interference ability and stability, and being able to work reliably in different working environments, with high stability.

[0027] Third, by adjusting the signal level of the control terminal, the present circuit can conveniently control the conduction state of the field effect transistor and the gate charging rate, meeting different application requirements and having the advantage of flexible control. Description of the Drawings

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings.

[0029] Figure 1 is the control circuit diagram of the present invention. Detailed Embodiments

[0030] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described by referring to the drawings below are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0031] Refer to Figure 1 to describe a control method for improving the turn-on current of a field-effect transistor according to an embodiment of the present invention, including the following steps.

[0032] Connect the first VCC terminal to the OUT terminal through the field-effect transistor Q1.

[0033] Form a control path by connecting the collector of the triode Q2 to the gate of the field-effect transistor Q1.

[0034] Apply the control signal of the control terminal to the base of the triode Q2 to adjust the conduction state of the field-effect transistor Q1.

[0035] Control the current path of the gate of the field-effect transistor Q1 through the conduction and cutoff of the triode Q2.

[0036] Working principle of the control method of the present invention: Connecting the first VCC terminal to the OUT terminal through the field-effect transistor Q1 realizes the current path from the power supply to the output terminal. The conduction state of the field-effect transistor Q1 is controlled by the triode Q2. The collector of the triode Q2 is connected to the gate of the field-effect transistor Q1 to form a control path. When the control signal of the control terminal is applied to the base of the triode Q2, the conduction state of the field-effect transistor Q1 can be adjusted to control the conduction state of the field-effect transistor Q1.

[0037] In addition, the conduction and cutoff of the triode Q2 can control the current path of the gate of the field-effect transistor Q1. When the triode Q2 is conducting, the current of the gate of the field-effect transistor Q1 can flow to the ground through the triode Q2, thereby changing the gate potential of the field-effect transistor Q1 and affecting its conduction state. When the triode Q2 is cutoff, the current of the gate of the field-effect transistor Q1 is provided by the external circuit to keep it in the conducting or off state.

[0038] By adjusting the signal level at the control terminal, the conduction degree of the triode Q2 can be controlled in this circuit. When the signal level at the control terminal increases, the conduction degree of the triode Q2 increases, and the current path change at the gate of the field-effect transistor Q1 speeds up, thus accelerating the turn-off process of the field-effect transistor Q1. When the signal level at the control terminal decreases, the conduction degree of the triode Q2 decreases, the current path change at the gate of the field-effect transistor Q1 slows down, and the gate charging rate of the field-effect transistor Q1 will also change accordingly, playing a role in controlling the gate charging rate of the field-effect transistor by adjusting the control signal level.

[0039] The circuit states under the high-level and low-level controls of the present invention are as follows: 1. High-level control: When a high level is applied to the control terminal, the triode Q2 conducts. Due to the conduction of the triode Q2, the potential of its collector decreases, thereby pulling down the potential of the gate of the field-effect transistor Q1. After the potential of the gate of the field-effect transistor Q1 decreases, the internal electric field distribution changes, causing the on-resistance of the field-effect transistor Q1 to increase and the current to decrease, accelerating the turn-off process of the field-effect transistor Q1.

[0040] 2. Low-level control: When a low level is applied to the control terminal, the triode Q2 is cut off. At this time, the gate current of the field-effect transistor Q1 is provided by an external circuit, enabling the field-effect transistor Q1 to maintain the on state, thereby realizing the current conduction between the first VCC terminal and the OUT terminal.

[0041] Specifically further, a third resistor R3 is provided between the base of the triode Q2 and the control terminal to limit the drive current input to the base of the triode Q2.

[0042] Specifically further, a fourth resistor R4 is connected in parallel between the base and the emitter of the triode Q2 to provide a path for discharging the base bias current of the triode Q2.

[0043] Specifically further, the gate of the field-effect transistor Q1 is connected to the collector of the triode Q2 through the second resistor R2 to adjust the gate drive impedance of the field-effect transistor Q1.

[0044] Specifically further, a second capacitor C2 is provided between the first VCC terminal and the ground for power supply filtering, and a third capacitor C3 is provided between the OUT terminal and the ground for output terminal filtering.

[0045] Specifically further, by adjusting the signal level at the control terminal, the conduction degree of the triode Q2 is controlled, and further, the gate charging rate of the field-effect transistor Q1 is controlled.

[0046] Specifically further, when a high level is applied to the control terminal, the triode Q2 conducts and pulls down the potential of the gate of the field-effect transistor Q1, accelerating the turn-off process of the field-effect transistor Q1.

[0047] Specifically further, when a low level is applied to the control terminal, the triode Q2 is cut off, and a conduction current is provided for the gate of the field effect transistor Q1 through an external circuit.

[0048] Meanwhile, the present invention also provides a control circuit applying the above control method for improving the turn-on current of a field effect transistor, including a first VCC terminal and an OUT terminal. The VCC terminal and the OUT terminal are connected through a field effect transistor Q1, and further includes a triode Q2. The gate of the field effect transistor Q1 is connected to the collector of the triode Q2, and the base of the triode Q2 is connected to a control terminal.

[0049] Specifically further, a third resistor R3 is connected between the base of the triode Q2 and the control terminal. A fourth resistor R4 is connected between the base and the emitter of the triode Q2. The gate of the field effect transistor Q1 is connected to the collector of the triode Q2 through a second resistor R2. One end of a second capacitor C2 is connected to the first VCC terminal, and one end of the second capacitor C2 is connected to a ground terminal GND. One end of a third capacitor C3 is connected to the OUT terminal, and the other end of the third capacitor C3 is connected to the ground terminal GND.

[0050] This circuit reduces current impact, reduces losses in the circuit, improves the service life of the field effect transistor and improves the turn-on current characteristics by precisely controlling the conduction and cut-off processes of the field effect transistor Q1. In addition, a first resistor R1 and a first capacitor C1 are reasonably arranged on the field effect transistor Q1, so that the circuit has good anti-interference ability and stability, can work reliably in different working environments, and has high stability. Furthermore, by adjusting the signal level of the control terminal, this circuit can conveniently control the conduction state of the field effect transistor and the gate charging rate, meet different application requirements and has the advantage of flexible control.

[0051] The basic characteristics of the field effect transistor and the triode in this circuit are as follows.

[0052] The field effect transistor Q1 is a voltage-controlled device, which controls the current between the drain and the source by changing the voltage between the gate and the source. The field effect transistor Q1 has the advantages of high input impedance, low noise, low power consumption, etc. In this control circuit, the field effect transistor Q1 plays a role in connecting the first VCC terminal and the OUT terminal, and the adjustment of its conduction state directly affects the output characteristics of the circuit.

[0053] The triode Q2 is a current-controlled device, which controls the current between the collector and the emitter by the base current. In this circuit, the triode Q2 is mainly used to control the conduction state of the field effect transistor Q1. The triode has two working states: amplification and switching. By applying different control signals to its base, it can be made to be in a conduction or cut-off state.

[0054] This control circuit includes a first VCC terminal, an OUT terminal, a field effect transistor Q1, and a triode Q2. The first VCC terminal and the OUT terminal are connected through the field effect transistor Q1. The gate of the field effect transistor Q1 is connected to the collector of the triode Q2, and the base of the triode Q2 is connected to a control terminal. In addition, a plurality of resistors and capacitors are provided in the circuit to achieve different functions.

[0055] Among them, the third resistor R3 is arranged between the base of the triode Q2 and the control terminal, and its main function is to limit the drive current input to the base of the triode Q2. When a signal is applied to the control terminal, R3 can prevent excessive current from flowing into the base of the triode Q2, thereby protecting the triode Q2 from being damaged.

[0056] The fourth resistor R4 is connected in parallel between the base and the emitter of the triode Q2, and it provides a discharge path for the base bias current of the triode Q2. When the triode Q2 is cut off, R4 can discharge the residual charge at the base to ensure that the triode Q2 can be reliably cut off.

[0057] The second resistor R2 is connected between the gate of the field effect transistor Q1 and the collector of the triode Q2, and is used to adjust the gate drive impedance of the field effect transistor Q1. By reasonably selecting the resistance value of the second resistor R2, the drive signal of the field effect transistor Q1 can be optimized to enable it to work more stably.

[0058] The second capacitor C2 is arranged between the first VCC terminal and the ground, and is mainly used for power supply filtering. It can filter out high-frequency noise and ripple in the power supply, provide a stable power supply voltage for the circuit, and ensure that the field effect transistor Q1 and the triode Q2 can work normally.

[0059] The third capacitor C3 is arranged between the OUT terminal and the ground, and is used for output filtering. It can smooth the output voltage of the OUT terminal, reduce the noise and fluctuation in the output signal, and improve the output quality of the circuit.

[0060] The resistance value of the third resistor R3 is 1 kΩ to 10 kΩ, which is used to limit the drive current to a safe range. For example, preferably, the resistance value of the third resistor R3 is 2 kΩ, which is used to limit the drive current of the control terminal within 5 mA. The capacitance value of the second capacitor C2 is 0.1 μF to 10 μF, which is used to filter out high-frequency noise. For example, preferably, the second capacitor C2 selects a 4.7 μF ceramic capacitor and is connected in parallel between the first VCC terminal and the ground to filter out the high-frequency noise of the power supply.

[0061] The advantages of this circuit are as follows.

[0062] First, improve the turn-on current characteristics: By precisely controlling the on and off processes of the field effect transistor, the current impact is reduced, the loss in the circuit is lowered, and the service life of the field effect transistor is increased.

[0063] II. High stability: The reasonable setting of resistors and capacitors enables the circuit to have good anti-interference ability and stability, and can work reliably under different working environments.

[0064] III. Flexible control: By adjusting the signal level of the control terminal, the on-state of the field-effect transistor and the gate charging rate can be conveniently controlled to meet different application requirements.

[0065] The application scenarios of this circuit are as follows: This control circuit is applicable to various occasions that require precise control of the on-current of the field-effect transistor, such as switching power supplies, motor drives, power amplifiers, etc. In a switching power supply, by improving the on-current characteristics of the field-effect transistor, the efficiency and stability of the power supply can be improved; in a motor drive, the current impact during motor startup can be reduced to protect the motor and the drive circuit.

[0066] The control method for improving the on-current of the field-effect transistor and the control circuit applying this method proposed by the present invention achieve precise control of the on-current of the field-effect transistor by reasonably utilizing the characteristics of the field-effect transistor Q1 and the triode Q2 and combining the functions of resistors and capacitors. This circuit has the advantages of high stability and flexible control, can effectively improve the working performance of the field-effect transistor, reduce the losses in the circuit, and improve the reliability and efficiency of electronic devices. In future electronic circuit designs, this control method and circuit have broad application prospects.

[0067] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for improving the control of the turn-on current of a field effect tube, the method comprising the following steps: Connect the first VCC terminal to the OUT terminal through the field effect transistor Q1; A control path is formed by connecting the collector of transistor Q2 to the gate of field effect transistor Q1; Applying a control signal from the control terminal to the base of the transistor Q2 to adjust the conduction state of the field effect transistor Q1; The current path of the gate of the field effect transistor Q1 is controlled by the conduction and cutoff of the transistor Q2.

2. The method for improving the control of the field effect tube turn-on current according to claim 1, characterized in that: A third resistor R3 is disposed between the base of the transistor Q2 and the control terminal to limit the driving current input to the base of the transistor Q2.

3. The method for improving the control of the turn-on current of a field effect tube according to claim 1, characterized in that: A fourth resistor R4 is connected in parallel between the base and emitter of the transistor Q2 to provide a base bias current discharge path for the transistor Q2.

4. The method for improving the control of the field effect tube turn-on current according to claim 1, characterized in that: The gate of the field effect transistor Q1 and the collector of the transistor Q2 are connected via the second resistor R2 to adjust the gate driving impedance of the field effect transistor Q1.

5. The method for improving the control of the turn-on current of a field effect tube according to claim 1, characterized in that: A second capacitor C2 is arranged between the first VCC terminal and the ground for power supply filtering, and a third capacitor C3 is arranged between the OUT terminal and the ground for output terminal filtering.

6. The method for improving the control of the turn-on current of a field effect tube according to claim 1, characterized in that: The conduction degree of transistor Q2 is controlled by adjusting the signal level at the control terminal, thereby controlling the gate charging rate of field effect transistor Q1.

7. The method for improving the control of the field effect tube turn-on current according to claim 6, characterized in that: When a high level is applied to the control terminal, the transistor Q2 is turned on and pulls down the gate potential of the field effect transistor Q1, accelerating the shutdown process of the field effect transistor Q1.

8. The method for improving the control of the turn-on current of a field effect tube according to claim 6, characterized in that: When a low level is applied to the control terminal, the transistor Q2 is turned off, and a conduction current is provided to the gate of the field effect transistor Q1 through an external circuit.

9. A control circuit using the method for improving the control of the turn-on current of a field effect tube according to any one of claims 1 to 8, comprising a first VCC terminal and an OUT terminal, characterized in that: The VCC terminal and the OUT terminal are connected via a field effect transistor Q1 , and further include a transistor Q2 . The gate of the field effect transistor Q1 is connected to the collector of the transistor Q2 , and the base of the transistor Q2 is connected to the control terminal.

10. The control circuit according to claim 9, characterized in that: A third resistor R3 is passed between the base of the transistor Q2 and the control terminal, a fourth resistor R4 is connected between the base and the emitter of the transistor Q2, the gate of the field effect transistor Q1 and the collector of the transistor Q2 are connected through a second resistor R2, the first VCC terminal is connected to one end of the second capacitor C2, one end of the second capacitor C2 is connected to the ground terminal GND, the OUT terminal is connected to one end of the third capacitor C3, and the other end of the third capacitor C3 is connected to the ground terminal GND.

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