Patent ID: 6320465
Filing Date: 2001-11-20
Classification: H03F,H03G

Abstract:
A method for limiting duty-cycle in a class-D amplifier comprising:limiting a maximum amplitude of an analog input signal;amplifying the amplitude limited analog input signal using an amplifier for providing a digital output signal switching between two voltages, each switched voltage corresponding to a voltage of a respective supply rail of an output power stage of the amplifier less a voltage drop on a respective power device therein, with an average value representing an amplified replica of the amplitude limited analog input signal;regenerating an amplified analog signal using a low pass filter;feeding the digital output signal to an input of a threshold limiting circuit for generating a positive threshold voltage and a negative threshold voltage, each threshold voltage corresponding to a pre-defined fraction of the respective switched voltages that the digital output signal switches to; andlimiting the maximum amplitude of the analog input signal to the positive threshold voltage and the negative threshold voltage.