High efficiency class D amplifier with reduced generation of EMI

A class D amplifier, comprising:

• a signal processing block configured to:
• generate a first processed signal representing a difference between a first differential signal and a second differential signal when a duty cycle of the first differential signal is greater than a duty cycle of the second differential signal, and being generated to have a pulse representing more than a period of time from a rising edge of the first differential signal to a rising edge of the second differential signal,
• generate the first processed signal representing a reference DC level when the duty cycle of the first differential signal is less than the duty cycle of the second differential signal,
• generate a second processed signal representing a difference between the second differential signal and the first differential signal when the duty cycle of the second differential signal is greater than the duty cycle of the first differential signal, and being generated to have a pulse representing more than a period of time from a rising edge of the second differential signal to a rising edge of the first differential signal, and
• generate the second processed signal representing the reference DC level, when the duty cycle of the second differential signal is less than the duty cycle of the first differential signal.

A method of amplifying an analog audio signal, comprising:

• receiving a first analog signal, the first analog signal being the analog signal;
• receiving a second analog signal, the second analog signal being a complement of the analog signal;
• converting the first and second analog input signals into first and second square waves;
• generating a first processed signal representing a difference between the first square wave and the second square wave when a duty cycle of the first square wave is greater than a duty cycle of the second square wave, and being generated to have a pulse representing more than a period of time from a rising edge of the first square wave to a rising edge of the second square wave;
• generating the first processed signal as a reference DC level, when the duty cycle of the first square wave is less than the duty cycle of the second square wave;
• generating a second processed signal representing a difference between the second square wave and the first square wave when the duty cycle of the second square wave is greater than the duty cycle of the first square wave, and being generated to have a pulse representing more than a period of time from a rising edge of the second square wave to a rising edge of the first square wave;
• generating the second processed signal as the reference DC level, when the duty cycle of the second square wave is less than the duty cycle of the first square wave;
• and
• generating first and second output signals respectively based upon the first and second processed signals, using respective first and second output stages.

An electronic device, comprising:

• first and second comparators configured to respectively convert first and second analog audio input signals into first and second audio square waves;
• a logic block coupled to receive the first and second audio square waves from the first and second comparators and configured to:
• generate a first processed audio signal having a pulse representing twice a period of time from a rising edge of the first audio square wave to a rising edge of the second audio square wave when a duty cycle of the first audio square wave is greater than a duty cycle of the second audio square wave,
• generate the first processed audio signal having a reference DC level when the duty cycle of the first audio square wave is less than the duty cycle of the second audio square wave,
• generate a second processed audio signal having a pulse representing twice a period of time from a rising edge of the second audio square wave to a rising edge of the first audio square wave when the duty cycle of the second audio square wave is greater than the duty cycle of the first audio square wave, and
• generate the second processed audio signal having the reference DC level when the duty cycle of the second audio square wave is less than the duty cycle of the first audio square wave;
• and
• first and second output stages coupled to the logic block and configured to generate first and second audio output signals respectively based upon the first and second processed audio signals.

An electronic device, comprising:

• first and second comparators configured to respectively convert first and second analog audio input signals into first and second audio square waves by comparing the first and second analog audio input signals to a sawtooth wave;
• a logic block coupled to receive the first and second audio square waves from the first and second comparators and configured to:
• generate a first processed audio signal representing a difference between the first audio square wave and the second audio square wave when a duty cycle of the first audio square wave is greater than a duty cycle of the second audio square wave, and being generated to have a pulse representing a period of time from a rising edge of the first audio square wave to a rising edge of the second audio square wave,
• generate the first processed audio signal having a reference DC level when the duty cycle of the first audio square wave is less than the duty cycle of the second audio square wave,
• generate a second processed audio signal representing a difference between the second audio square wave and the first audio square wave when the duty cycle of the second audio square wave is greater than the duty cycle of the first audio square wave, and being generated to have a pulse representing a period of time from a rising edge of the second audio square wave to a rising edge of the first audio square wave, and
• generate the second processed audio signal having the reference DC level when the duty cycle of the second audio square wave is less than the duty cycle of the first audio square wave;
• and
• first and second output stages coupled to the logic block and configured to generate first and second audio output signals respectively based upon the first and second processed audio signals.