Patent ID: 8280074
Filing Date: 2012-10-02
Classification: H03F,H03K

Abstract:
1. An audio signal processing circuit, connected in a BTL configuration directly or via a demodulation filter to a speaker, for outputting an input audio signal as a positive phase PWM signal and a negative phase PWM signal, said audio signal processing circuit comprising: a quantizer for quantizing an input digital audio signal into a low-resolution digital audio signal; a noise shaper for shifting quantization noise distribution of the low-resolution digital audio signal to a high frequency; a pattern comparator circuit for comparing patterns of a positive phase digital signal and a negative phase digital signal from the noise shaper when muting; a selector for outputting said positive phase digital signal and negative phase digital signal when patterns are judged not to match at said pattern comparator circuit and outputting a predetermined set value instead of said positive phase digital signal and said negative phase digital signal when patterns are judged to match; and a PWM modulator for PWM modulating and outputting said positive phase digital signal, said negative phase digital signal, and said set value output from said selector, wherein said set value is a value having 50% duty when PWM modulated at said PWM modulator.