A MULTIPHASE PULSE WIDTH MODULATOR FOR CLASS D AUDIO AMPLIFIERS

摘要

A multiphase pulse width modulator (PWM) producing N mutually phase shifted PWM signals, which is well-suited for class D audio amplifier applications. The multiphase PWM includes (a) N+1 (N≧2) analog triangular waveform generators producing N+1 mutually phase shifted triangular waveforms, and (b) N+1 comparators each having a first input coupled to each of the N+1 triangular waveforms and a second input coupled to an audio signal to generate N+1 mutually phase shifted PWM phase signals. A crosspoint switch includes N+1 inputs coupled to the N+1 PWM phase signals, and N outputs to supply the N PWM signals. A crosspoint switch controller selectively connects each of the N+1 inputs to each of the N outputs for a duration of a cycle time in a time sequence to simultaneously generate the N PWM signals such that each signal has interleaved time segments of the N+1 PWM phase signals.

主权项

1. A multiphase pulse width modulator producing N mutually phase shifted pulse width modulated signals having a predetermined cycle time for class D audio amplifiers, comprising:
N+1 analog triangular waveform generators configured to produce respective N+1 mutually phase shifted analog triangular waveforms each comprising a rising segment with substantially linearly increasing signal amplitude, a falling segment with substantially linearly decreasing signal amplitude and an idle signal segment with substantially constant signal amplitude such that a duration of the rising segment and falling segments corresponds to the predetermined cycle time and a duration of the idle segment corresponds to a phase shift between two adjacent phases of the N mutually phase shifted pulse width modulated signals, N+1 comparators each comprising a first input operatively coupled to respective ones of the N+1 mutually phase shifted analog triangular waveforms and a second input coupled to an audio signal to generate at least N+1 mutually phase shifted pulse width modulated phase signals; a crosspoint or matrix switch comprising N+1 input terminals, coupled to respective ones of the N+1 mutually phase shifted pulse width modulated phase signals, and N output terminals configured for supplying respective ones of the N mutually phase shifted pulse width modulated signals, a crosspoint switch controller configured to: selectively connect each of the N+1 input terminals to each output terminal of the N output terminals for a duration of the predetermined cycle time in a predetermined time sequence to simultaneously generate the N mutually phase shifted pulse width modulated signals such that each of the signals comprises interleaved time segments of the N+1 mutually phase shifted pulse width modulated phase signals; N being a positive integer larger than or equal to 2.