APPARATUS AND METHOD FOR GENERATING WAVEFORMS WHICAPPARATUS AND METHOD FOR GENERATING WAFEFORMS WHICH ARE PARTICULARLY SUITABLE FOR A PWM DRIVEN MOTOR

摘要

A triangle waveform having substantially linearly sloped, gradually increasing and decreasing edges and having a frequency nf is generated from an n-phase sine wave signal, each phase having a fundamental frequency f. A segment of any of the n-phases of the sine wave is detected when that segment is within a predetermined angular amount from a reference crossing level, such as the zero crossing of the sine wave signal. Successive ones of the detected segments are selected to synthesize the triangle waveform. In the preferred use of this invention, the triangle waveform is compared to a reference signal, such as the sine wave signal from which the triangle waveform is generated, this reference signal having a controllable frequency and amplitude. Pulse transitions are generated at the intersection of the triangle waveform and each of the respective phases of the reference signal. In one embodiment of this invention, the frequency of the triangle waveform is increased by an amplitude- folding technique wherein the triangle waveform (of frequency nf) is folded about a pair of equal but opposite folding levels whenever the triangle waveform reaches either of these levels, so as to produce an amplitude-folded triangle waveform of frequency mf and of peak levels determined by the folding levels.