PWM power amplifier with digital input

A digital input PWM power amplifier comprising:

• an input circuit receiving pulse code modulated (PCM) digital input data organized in words of a first number of M bits at a bit rate, and outputting PCM digital data organized in words of a smaller number of N bits at a multiple of the bit rate;
• a first bus transmitting a first number of most significant bits (MSBs) of the N bit words output from said input circuit, and a second bus transmitting a second number of least significant bits (LSBs) of the N bit words output from said input circuit;
• first and second converters respectively fed from said first and second buses, each converter comprising
• a counter driven by a clock signal having a frequency equal to the product of the bit rate of the MSBs or LSBs transmitted on the respective buses times the base two raised to the respective first or second number of MSBs and LSBs, and
• a digital comparator receiving through a first input the reference digital words and through a second input the respective first or second number of MSBs and LSBs, and outputting a respective PWM signal;
• and
• an output power stage having an input receiving a driving signal defined by a PWM signal output by said first converter summed with an attenuated PWM signal output by said second converter.

A method for converting a PCM signal to a PWM signal for a PWM power amplifier comprising the steps of:

• dividing the PCM signal comprising words of a first number of M bits at a bit rate into words of a smaller number of N bits at a multiple of the bit rate;
• transmitting a first number of most significant bits (MSBs) of the N bit words on a first bus, and transmitting a second number of least significant bits (LSBs) of the N bit words on a second bus;
• driving a pair of counters by respective clock signals having a frequency equal to the product of the bit rate of the MSBs or LSBs transmitted on the respective buses times the base two raised to the respective first and second number of bits for generating reference digital words;
• and
• generating a driving signal based upon the pair of counter.