Patent ID: 8116368

Claim:
A PWM signal generator comprising: a first PCM signal that is input into the PWM signal generator, the first PCM signal having a first sampling period; a second PCM signal having a second sampling period, wherein the second sampling period is varied for each sampling period so that the same period may consecutively appear, according to an external instruction or a predetermined sequence, and a resolution of the second PCM signal is coarser than that of the first PCM signal; a delta-sigma modulator that converts the first PCM signal into the second PCM signal, the delta-sigma modulator including a filter and a quantizer, wherein the first PCM signal and the second PCM signal are input into the filter, which then outputs a third PCM signal, and the quantizer converts the third PCM signal into the second PCM signal and a gain of the quantizer is dynamically varied in proportion to a value of the second sampling period, and a set of coefficients and a set of functions for an internal calculation in the filter are determined and dynamically varied according to the second sampling period; and a PWM signal that is output from the PWM signal generator, wherein the PWM signal is generated by digital means based on the second PCM signal.