Application of spread spectrum for EMI reduction in class D amplifier

A spread spectrum technique and apparatus for reducing electromagnetic interference (EMI) in class D amplifier are introduced. The technique utilizes very simple hardware, where the switching frequency of a class D amplifier is dynamically varied from 1 to 1.22MHz. This is achieved by changing the charging current of an oscillator in a random fashion, through 6 switches that are controlled by 6 random digital signals. Compared to fixed frequency operation, the spectrum of a switching signal was greatly flattened and a reduction of 6dB in the EMI without efficiency and performance degradations was obtained.