Design Of The GaN Device Based BLDC Driver In The Field Of Power Tools

The brushless direct current(BLDC)motor has become the preferred choice for the electric power tools,because of its high power density,high energy conversion efficiency and low maintenance cost.The performance of the BLDC driver is critical to improve the efficiency of the electric power tools,which should has high rotation speed,high level of integration,and high power of resisting voltaic impingement.However,the traditional silicon technology based switch driver has drawbacks of low power density,low switch frequency,high switching loss,which becomes a blocking factor for the BLDC motor to evolve towards higher speed.Therefore,it is of great significance to develop a new generation of BLDC driver with higher performance which is suitable for higher speed power tools.Firstly,the system architecture and components of power tool is introduced to give a sense of the importance of the BLDC motor and its switch driver to the power tools.After that a theoretical model is built which focuses on the topology structure and commutation logic.A simulation model for the BLDC motor is built using Matlab/Simulink toolbox,the performance under different PWM duty cycle is simulated to verify the correctness of the theoretical model.Secondly,for the insufficient performance of silicon transistor,a new solution to the BLDC switch driver based on Ga N transistor is proposed.Based on the discussion of the characteristics of Ga N transistor,,a signal model for the Ga N transistor is constructed,and the calculation procedure of the driving resistance for grid electrode is derived.A double pulse test platform based on LTspice software is designed to evaluate the switching performance of Ga N transistor.and the correctness of the driving resistance calculation is verified,which provides the design basis for the practical application of Ga N transistor.Finally,a new BLDC driver based on Ga N transistor is designed,the hardware and software design is presented in detail.A sample driver module is built and tested.Test results show that the Ga N transistor based solution reduces the size of the BLDC driver greatly.The interval of switching time is decreased to 40 ns and the switching loss is saved,and the switching frequency of PWM can be up to 200 k Hz.The designed Ga N transistor based BLDC driver meets the needs of high speed power tools.