There is a circuit for fast shut-off of MOS tube. Does anyone know the specific working principle? How to shut down quickly?

QWE4562009

There is a circuit for fast shut-off of MOS tube. Does anyone know the specific working principle? How to shut down quickly? [Copy link]

 

There is a circuit for fast shut-off of MOS tube. Does anyone know the specific working principle? How to shut down quickly?

okhxyyo

Is this circuit complete?

QWE4562009

okhxyyo posted on 2021-1-25 14:46 Is this circuit complete?

The drive part is like this

QWE4562009

QWE4562009 posted on 2021-1-25 16:35 The driver part is like this

Is this post going to be forgotten?

QWE4562009

okhxyyo posted on 2021-1-25 14:46 Is this circuit complete?

CO comes from the microcontroller. When CO is high, Q2 is turned on. Since Q1 is always turned on, what is the meaning of Q1? Or does Q1 only turn on when CO is high? This is a circuit that accelerates the MOS off, but it does not show how fast it is.

LuJianchang

QWE4562009 Published on 2021-1-26 14:18 CO comes from the microcontroller. When CO is high, Q2 is turned on. Since Q1 is always turned on, what is the meaning of Q1? Also...

The answer you want can be found in Chapter 10 of this chip document

QWE4562009

LuJianchang posted on 2021-1-27 10:22 You can find the answer you want in Chapter 10 of this chip document

What does this document describe?

QWE4562009

LuJianchang posted on 2021-1-27 10:22 You can find the answer you want in Chapter 10 of this chip document

This is the complete circuit provided by CW

maychang

QWE4562009 posted on 2021-1-31 09:47 This is the complete circuit provided by CW

The circuit that accelerates the shutdown of the MOS tube is in the red box.

maychang

QWE4562009 posted on 2021-1-31 09:47 This is the complete circuit provided by CW

To quickly shut down the MOS tube, the key device is the bipolar transistor in the blue circle.

QWE4562009

maychang published on 2021-1-31 11:13 To make the MOS tube turn off quickly, the key device is the bipolar transistor in the blue circle.

Using VBE to discharge quickly?

maychang

QWE4562009 posted on 2021-1-31 14:38 Using VBE for fast discharge?

"Using VBE to discharge quickly?"

If VBE is used for discharge, why use a transistor? Can't a diode be used?

It uses the amplification effect of the transistor to make the MOS tube gate discharge quickly.

QWE4562009

maychang posted on 2021-1-31 14:42 "Using VBE to discharge quickly? " If VBE is used for discharge, why use a transistor? Isn't it enough to use a diode? It is the discharge of the transistor...

Amplify the VGS of MOS?

maychang

QWE4562009 posted on 2021-2-1 10:46 Enlarge the VGS of MOS?

Bipolar transistors are current-mode devices.

The transistor in this circuit amplifies the MOS tube gate discharge current.

maychang

QWE4562009 posted on 2021-2-1 10:46 Enlarge the VGS of MOS?

"Amplify the VGS of MOS?"

The bipolar transistor in this circuit cannot be replaced by a field effect transistor. Based on this point, it is clear that the voltage is not amplified.

QWE4562009

maychang posted on 2021-2-1 11:26 "Amplify the VGS of MOS?" The bipolar transistor in this circuit cannot be replaced by a field effect transistor. Based on this point, it is clear that it is not amplifying the voltage...

What is the direction of the gate current? Can it be amplified? Can it speed up the MOS shutdown?

maychang

QWE4562009 posted on 2021-2-2 11:50 What is the direction of the gate current? Amplify the current? Can it speed up the MOS shutdown?

I suggest you first read the "Zero-state response of a first-order circuit" and "Zero-input response of a first-order circuit" in the "Circuit" textbook, and then figure out the workings of the power MOS tube before discussing the use of bipolar transistors to accelerate the turn-off of the MOS tube. Without these basic knowledge, it is impossible to discuss.

LuJianchang

First of all, you need to know that there is parasitic capacitance between the three poles of the MOS tube. The function of the PNP transistor is to quickly discharge the parasitic capacitance between the GS poles of the MOS tube.

maychang

LuJianchang published on 2021-2-3 10:49 First of all, you need to know that there are parasitic capacitances between the three poles of the MOS tube. The function of the PNP transistor is to quickly discharge the parasitic capacitance between the GS poles of the MOS tube.

This PNP transistor not only discharges the parasitic capacitance between the GS poles of the MOS tube, but also discharges the Miller capacitance of the MOS tube working in the common source state.

LuJianchang

maychang published on 2021-2-3 12:22 This PNP transistor not only discharges the parasitic capacitance between the GS poles of the MOS tube, but also discharges the Miller capacitance of the MOS tube working in the common source state.

Does Miller capacitance refer to Cgd?