PWM converting circuit, D/A converter and PWM converting method with improved resolution

A D/A converter comprising a PWM converting circuit and a low-pass filter for carrying out waveform shaping of a PWM signal output from said PWM converting circuit, said PWM converting circuit carrying out PWM conversion of each value of digital input data for each predetermined number of bits of a basic clock pulse train, and outputting conversion result as a PWM signal, said PWM converting circuit comprising:

• a pulse generator for generating two pulse signals taking one of a low level and a high level for each bit of the basic clock pulse train in response to the value of the digital input data;
• and
• a differential amplifier for outputting a differential amplification component between the two pulse signals as the PWM signal, wherein
• said pulse generator varies a pulse width of one of the two pulse signals on a bit-by-bit basis of the basic clock pulse train in response to the value of the digital input data, and holds a level of the other of the two pulse signals throughout the predetermined number of bits of the basic clock pulse train.

A PWM converting method that carries out PWM conversion of each value of digital input data for each predetermined number of bits of a basic clock pulse train, and outputs the conversion result as a PWM signal, said PWM converting method comprising the steps of:

• generating two pulse signals taking one of a low level and a high level for each bit of the basic clock pulse train in response to the value of the digital input data;
• varying a pulse width of one of the two pulse signals on a bit-by-bit basis of the basic clock pulse train in response to the value of the digital input data;
• holding a level of the other of the two pulse signals throughout the predetermined number of bits of the basic clock pulse train;
• and
• outputting a differential amplification component between the two pulse signals as the PWM signal.