Patent ID: 7486122
Filing Date: 2009-02-03
Classification: G06F,H03K

Abstract:
1. A digitized pulse width modulation (PWM) signal generation method for generating N-phase PWM signals, wherein each phase PWM signal has a same period, and a phase difference between the PWM signals is said period being divided by N or is 0, wherein N is a positive integer greater than or equal to 3, the digitized PWM signal generation method comprising: providing a plurality of reference levels, wherein a voltage value of each reference level is between a first voltage value and a second voltage value, and the reference levels are used for determining a duty cycle of the PWM signals correspondingly; providing a common PWM carrier, wherein the common PWM carrier is a plurality of fixed-cycle sawtooth signals, and the common PWM carrier has N fixed-cycle sawtooth signals during the switch period of each phase PWM signal; providing a plurality of first (N−1)-step digital staircase signals, wherein a third voltage level state of each step digital staircase in each of the first (N−1)-step digital staircase signals is updated at a reset edge of each fixed-cycle sawtooth signal according to the state of each phase PWM signal; amplifying the reference levels N times, and then subtracting the amplified reference levels from the third voltage level of each step digital staircase in each of the first (N−1)-step digital staircase signals to obtain a plurality of second (N−1)-step digital staircase signals correspondingly; restricting a fourth voltage level state of each step digital staircase in each of the second (N−1)-step digital staircase signals between the first voltage value and the second voltage value; and comparing the restricted fourth voltage level state of each step digital staircase in each of the second (N−1)-step digital staircase signals with a fifth voltage level of the fixed-cycle sawtooth signals during the switch period of each phase PWM signal to generate the N-phase PWM signals correspondingly.