MOS tube DS short circuit

ABC159753

MOS tube DS short circuit [Copy link]

 

 

When using a P-type MOS tube, what happens when the DS ends are short-circuited when the power is on and the load is added? The voltage is added to 28V, the load is 2.5A, and it is used in an overcurrent protection circuit. It is turned off after overcurrent, but the MOS tube is always burned.

wang12011201

"When using a P-type MOS tube, what happens when the DS ends are short-circuited when the power is on and the load is added? The voltage is added to 28V, the load is 2.5A, and it is used in an overcurrent protection circuit. It is shut down after overcurrent, but the MOS tube always burns out."

beyond_笑谈

The main phenomenon after MOSFET failure is DS short circuit. According to the description, it should be thermal breakdown, and MOSFET should enhance heat dissipation.

qwqwqw2088

The selected MOS tube can withstand a continuous current of 2.5A.
The voltage of 28V may exceed the maximum drain-source voltage (Vds_max) of the MOS tube.

You should choose a MOS tube with a higher breakdown voltage.

ABC159753

beyond_笑谈Published on 2024-10-8 10:40 The main phenomenon after MOSFET failure is DS short circuit. According to the description, it should be thermal breakdown. MOSFET strengthens heat dissipation.

When the MOS tube was broken down, the temperature was about 40 degrees.

ABC159753

beyond_笑谈Published on 2024-10-8 10:40 The main phenomenon after MOSFET failure is DS short circuit. According to the description, it should be thermal breakdown. MOSFET strengthens heat dissipation.

The circuit diagram is as follows. The MOS tube is WSD86P10DN56, and the parameters are as follows

ABC159753

qwqwqw2088 posted on 2024-10-8 10:52 The selected MOS tube can withstand a continuous current of 2.5A. The voltage of 28V may exceed the maximum drain-source voltage (Vds_max) of the MOS tube. To select...

I chose 100V VDS and 17mΩ internal resistance. I tried it several times and it lasted for tens of seconds each time.

The MOS tube is smoking and the DS is short-circuited. Could you please tell me what is going on?

zdb9

What type of load is it? If it is an inductive load, a freewheeling diode or RC snubber circuit should be added at both ends of the load to absorb the electromagnetic energy generated when it is disconnected and prevent the induced voltage from breaking down the MOS tube.

ABC159753

zdb9 posted on 2024-10-8 11:07 What type of load is it? If it is an inductive load, a freewheeling diode or RC snubber circuit should be added at both ends of the load to easily absorb the electromagnetic energy generated when disconnected, ...

It is the electronic load constant current CC 2.5A load

xiayichuyang123

It is recommended to check the drive waveform to see if there is incomplete conduction.

呜呼哀哉

ABC159753 posted on 2024-10-8 10:59 The circuit diagram is like this, the MOS tube is WSD86P10DN56, the parameters are as follows

Judging from the voltage values of your various nodes, this VGS cannot turn on the MOS tube at all. The current flows through the body diode, which will definitely cause a temperature rise.

ABC159753

xiayichuyang123 posted on 2024-10-8 11:16 It is recommended to check the drive waveform to see if there is incomplete conduction

I have tested the voltage across GS before. The voltage was 12V when the MOS was removed at 2.4A. The voltage difference was 0 at 2.5A. It should be turned off at this time. However, just after the test, about 10 seconds, the MOS DS broke down.

ABC159753

ABC159753 posted on 2024-10-8 11:30 I have tested the voltage across GS before. The voltage was 12V after removing the mos at 2.4A. The voltage difference was 0 at 2.5A. It should be turned off at this time, but it is probably...

MOS tube can be fully turned on at 10V

ABC159753

Alas, published on 2024-10-8 11:30 Judging from the voltage values of your nodes, this VGS cannot turn on the MOS tube at all. The current flows through the body diode, and there will definitely be a temperature rise.

This is the simulated MOS tube off state. The actual device is different from the simulation. The circuit diagram is like this. When the actual load is 2.4A, the voltage across GS is 12V, and the MOS tube is fully turned on at 10V. There is no voltage difference across GS at 2.5A load. At this time, it should be turned off, but the MOS tube directly breaks down across SD.

chineseboyzxy

ABC159753 posted on 2024-10-8 10:59 The circuit diagram is like this, the MOS tube is WSD86P10DN56, the parameters are as follows

Your R13 is shown as 2 ohms. The transistor BE junction and the resistor are connected in parallel, so it can be turned on with only 0.3A current.

lansebuluo

The resistance value of R13 can be increased to test the function, action time and recovery time of the protection circuit without damaging the MOS.

聋门叨客

MOS is not a switch. You will make MOS work in the linear region and burn MOS. The design intention is understandable. The sampling resistor R13 is used to control the output of transistor Q4, and finally turn off MOS. The problem is that the VGS of MOS will not be turned off when it is lower than the conduction threshold, but it is still continuously turned on. At this time, the Rds of MOS will change linearly according to the driving voltage and finally make the output current reach a balanced value, and this value will not be 0. The output voltage is reduced, because after Rds increases, the voltage is divided on MOS, and MOS bears all the power consumption. The current that MOS can withstand is the safe zone composed of voltage and current when it is fully turned on, which does not mean that it can also withstand the linear zone. The thermal resistance of your package is 62°/W, which cannot even withstand 3W of power consumption. It is normal to burn.

ABC159753

Lunmendaoke published on 2024-10-9 10:59 MOS is not a switch. You will make MOS work in the linear region and burn MOS. The design intention is understandable. The sampling resistor R13 is used to control the transistor...

Could you please tell me how to modify it to avoid this situation?

振动试验仪器

When repairing the amplifier, first disconnect the DS voltage, add the GS voltage, and use an oscilloscope to check whether the GS voltage waveform is a square wave and that the duty cycle is correct.

After the GS voltage waveform is normal, add the DS voltage.