Abstract: MCU is the core component of variable frequency driving system. As vector control need a large number of complicated calculating and has a high requirement for real-time, the operation requirement of MCU for variable frequency driving control is analyzed firstly. The Cordic hardware coprocessor is applied for the complicated calculating of trigonometric function and square root. And to settle the problems of single resistance sampling and frequency reduction, which are unique in variable frequency driving of air-conditioning, some functions are designed, including double trigger and sampling delay of AD, flexible phase shift of PWM, interval skip of interrupt, etc. The basic resources and functions of MCU are also analyzed and designed for the general requirements. At last, the custom designed MCU is applied in air-conditioner products, through which related functions are verified.

Key words: Domestic MCU, Variable frequency driving, Requirements analysis, Customized design and application