Patent ID: 7113053

Claim:
In a pulse width modulation signal generating device that generates a pulse width modulation signal formed continuously from a plurality of unit pulse signals while changing a duty cycle by a predetermined duty change rate, where a period of a unit pulse signal formed from a first level and a second level continuous with said first level is a fixed period Tc, a pulse width modulation signal generating device comprising: a data storage device that stores a plurality of sets of data of an initial duty cycle, a duty change rate, and a count of unit pulse signals forming a phase for defining individual phases of a pulse width modulation signal; a data reading device that, when generating said pulse width modulation signal, reads said plurality of sets of data stored in said storage device, a selected initial duty cycle, a selected duty change rate, and a selected unit pulse signal count for a phase to be generated; a period timer repeatedly measuring said fixed period Tc; an arithmetic processor thus performs calculations wherein, in a first unit pulse signal said selected initial duty cycle is multiplied with said fixed period Tc, and in a second and subsequent unit pulse signals, said selected duty change rate is added to or subtracted from a duty cycle of an immediately preceding unit pulse signal with a duty cycle obtained by said addition or subtraction being multiplied with said fixed period Tc, resulting in a first level generating interval T 1 for each unit pulse signal; a PWM timer initiating a time measurement of said first level generating interval T 1 each time said period timer initiates a time measurement for said fixed period Tc; and a signal generating device wherein, when said period timer initiates a time measurement of said fixed period Tc, a signal level of said pulse width modulation signal is set to a first level and when said PWM timer measures said first level generating interval T 1 , said first level is changed to said second level, and said second level is maintained until said period timer measures said fixed period Tc; wherein said signal generating device continuously generates a number of unit pulse signals determined by said selected unit pulse signal count and generates a pulse width modulation signal for 1 phase.