Filterless class D amplifiers using spread spectrum PWM modulation

摘要

Filterless class D amplifier using spread spectrum pulse width modulation with feedback to suppress low frequency noise in the amplifier output. The amplifiers may use any of a wide variety of pulse width modulators with a dynamically variable frequency ramp or triangular waveform to whiten the output noise of the amplifier. Typically the ramp or triangular waveform input to the modulators is randomly or pseudo randomly varied over some percentage about a nominal frequency. Various feedback techniques for suppressing the low frequency noise are disclosed. Using this invention, Electromagnetic Interference (EMI) emissions from the circuit can be kept substantially below regulatory requirements without the need for expensive external filtering and/or shielding external to the integrated circuit.