How to quickly turn off the classic FET - Kia MOS transistor

mos Fast shut-off principle of tube
R4 yes Q1 The on resistance of is not Q1 There is no need to install , When the low potential comes Q1 To drain the diffuser .

power MOS How to turn it off ？ Can it be used PWM Realization , How to achieve ？
power mosfet The three ports of ,G extremely ,D extremely ,S extremely .G Pole control mosfet Opening of , Turn off , to GS Apply forward voltage between poles （ High level ）[url=13/], When the threshold value of the on voltage is reached, it can be turned on . Empathy ,[url=15/] Give a low voltage （ Low level ）mosfet Can turn off . Since it is high and low level, of course it can be used PWM Realization , But in specific applications , Consideration should be given PWM Output high and low level voltage range ,PWM Voltage output, driving ability, etc . The driving capacity is too small , Even if the voltage is high , Still can't drive to open MOS tube . You need to be in PWM The circuit is followed by PWM Drive circuit , Then control the power mosfet. This PWM It should have a negative pulse , Can quickly turn off MOS tube .

MOS The first principle of accelerating shutdown of tube is .R4 The role of . I don't understand .

It seems that Lou doesn't know the principle of triode , No, R4 How to satisfy Q1 Requirements for collector reverse bias （ Whether it's PNP still NPN triode , When it works, it must meet the reverse bias of collector junction , The emission junction is biased ）.D1 Apply a negative pulse before Q1 It turns on ,[url=31/] You can draw the current from the base , Speed up MOS The tube is off .D1 The function of is one-way conduction [url=32/], Do not divide the base current into pulse amplification circuits , Let the current go to ground . Do you understand ？

It can accelerate MOS The function of pipe shutdown , thank you

The driving resistance is mainly used to make MOS The tube turns on slightly slower , To avoid over driving , This benefit is to solve the radiation problem in electromagnetic compatibility , Parallel connection of a resistor is to accelerate the cut-off , Reduce MOS Turn off loss of tube .

MOS Fast shut-off principle of tube
R4 yes Q1 The on resistance of is not Q1 There is no need to install , When the low potential comes Q1 A brief analysis is made of the UC3637 double PWM Controller and IR2110 Characteristics , working principle . from UC3637 and IR2110 A high voltage, high power and small signal amplification circuit is constructed together , And pass .

MOS tube D1 The effect of accelerating the rising edge velocity of rectangular wave ？ I still don't understand this here .

This circuit is used to improve MOSFET Of the shut-off speed , Originally, the direct drive of logic gate is also very fast , However, it is possible that the maximum output current of the logic gate is not large enough , So you can use that PMOS Quick shutdown . At power MOSFET In circuit , Quick shut-off is more important in safety than being able to open quickly .

Asking questions MOS How to adjust the large shutdown delay ？
Make fun of the front level , Make fun of the lower level . That's all right. ... Break the front stage , test MOS Input level . If it's low, pull it up , High drop-down . Anyway, fight him . Then add the previous level . Give it a try . Adjust the resistance of the grid, ah, maybe .

How to speed up MOS Tube off
A follower can be added to the grid to drive the grid , It can shorten the switching time , Add a resistor or capacitor to the grid to discharge the process of field tube switching , The above are all ways to improve the switching speed ！！ The circuit is too small , Incomplete .

mos Tube as switch circuit ,5V Pick up G,S extremely , be D,S The pole is connected , But disconnect 5.
The pipe can be cut off quickly and smoothly only with grid leakage prevention circuit . Because there is a thin silicon dioxide insulating layer between the gate and the substrate , Therefore, there is a capacitance between the gate and the substrate . When G When the voltage is applied, the capacitor will be charged , When G If... After the voltage on the is removed G The charge of the suspended capacitor cannot be released immediately , actually G The voltage at the pole still exists for some time , So it won't end right away . In actual use, when the pipe is required to be cut off, it must be in GS Establish a relief circuit between （ Such as direct short circuit or discharge through resistance ） Can only be .

A triode and P-MOSFET A switching circuit composed of , Open normal , Turn off .

The equivalent capacitance is negligible relative to the switching circuit （ Unless the frequency is particularly high ）,MOS The pipe belongs to the pressure control element , For general switching circuits, the switching speed should be about the same .

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