The asymmetric regular sampling principle of PWM is researched in this paper and a simple method appropriate for online algorithm is provided,on basis of which,a FPGA-based digital method of phase-locked synchronous PWM modulator is presented. Both FPGA and ROM are used as programmable timer in the method.The switch fre- quency is high and fundamentally stable.The modulation ratio,phase,and frenquency can be controlled independentally,which is specially applicable to PWM reversible rectifier. As the whole s...