MOS drive in motor controller

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Universal MCU or DSP Of IO The voltage is usually 5V\3.3V,IO Its current output capacity is 20MA following , Insufficient direct drive power MOSFET. So use general MCU or DSP When designing motor drivers , It usually needs to be matched with external MOSFET Driver , We call it “ Pre drive ”. Designing automobile fans 、 Water pump 、 When the motor drives the controller such as oil pump , Use vehicle regulations MCU+ Vehicle gauge pre drive + Car rules N Channel power MOSFET, It can adapt to different power 、 Various communication modes and various driving modes .

Power in the controller MOS drive

     As shown in the above figure, brushless DC motor drive circuit , Three phase brushless DC motor （ Include BLDC and PMSM） The power stage drive circuit uses 6 individual N Channel power MOS Form a three-phase full bridge , It is divided into three connected to the positive pole of the power supply （VBus） The high side of the road MOS And three low sides connected to the negative pole of the power supply MOS.whaosoft aiot http://143ai.com

     The controller controls six MOS On and off of , Complete commutation , Make the motor rotate as expected . The motor may encounter blockage during operation, which will lead to overcurrent , therefore MOS The drive circuit needs to have a protection function , To prevent burning out the controller or motor ..

     For a single NMOS Come on , At the time of opening up , It is necessary to provide instantaneous high current to MOS Charge the parasitic capacitor inside , Gate source voltage （VGS） When a certain threshold is reached ,MOS Can be fully opened . stay MOS After opening , It is also necessary to maintain the appropriate gate source voltage （VGS）, Only in this way can it remain open .

     For low side MOS, Its source （S） Connected to the negative pole of the power supply , The gate source voltage is easy to meet , The drive is simple .

     For high side MOS, Its source （S） Connected to the motor phase line , The voltage is uncertain , If you need to open , The grid voltage needs to be supplied through the bootstrap circuit , The drive is complex .

     Above, VGS And RDSON Diagram for , In general ,MOS The internal resistance of the conduction is shown in the figure above , With VGS To increase and decrease , but VGS Greater than 10V after , The descent curve becomes gentle . In order to achieve the minimum on resistance (RDSON),VGS The value of is usually 10~15V. Yanqing Chuanbei community 45 Miss sun Collect and sell waste products and junk for stock speculation Waste sun Recycle