The role of the power MOS in the electric vehicle controller is very important. Simply speaking, the output current of the MOS is used to drive the motor. The larger the current output (in order to prevent overcurrent from burning out the MOS, the controller has a current-limiting protection), the stronger the motor torque and the stronger the acceleration (the torque before the motor's magnetic saturation is proportional to the phase current).
The working state of MOS in the controller circuit. Turn-on process (transition process from turn-on to turn-on), turn-on state, turn-off process (transition process from turn-on to turn-off), turn-off state, and an abnormal state, breakdown state (small energy current pulses are often Recoverable breakdown, i.e. MOS will not be damaged).
The main loss of MOS also corresponds to these states, switching loss (turn-on process and turn-off process), turn-on loss, turn-off loss (caused by leakage current, this is ignored), and avalanche energy loss. As long as these losses are controlled within the tolerance specification of the MOS, the MOS will work normally, and if it exceeds the tolerance range, damage will occur. The switching loss is often greater than the conduction state loss (the difference between different MOS may be very large), especially when the pwm is not fully turned on and is in the pulse width modulation state (corresponding to the starting acceleration state of the electric vehicle), and the highest rapid state is often conduction. Loss is dominant.
The main reasons for MOS damage: overcurrent, high temperature damage caused by high current (continuous high current and instantaneous super current pulse cause the junction temperature to exceed the withstand value); overvoltage, source-drain level is greater than the breakdown voltage and breakdown; gate breakdown , generally because the gate voltage is damaged by the outside world or the drive circuit exceeds the allowable maximum voltage (the gate voltage generally needs to be lower than 20v to be safe) and electrostatic damage.
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