Conversion of a single-bit signal into a PWM signal

A novel pulse width modulation (PWM) signal generation technique is proposed. The generator converts a single-bit digital signal into a PWM signal without a ramping waveform generator. The proposed PWM signal generators are based on the concept of Delta-Sigma (/spl Delta//spl Sigma/) modulation. A comparator with hysteresis is used instead of a quantizer in the /spl Delta//spl Sigma/ modulator. The switching frequency of the PWM signal decreased with increase of the hysteresis width. The noise-shaped output is obtained and a high signal to noise ratio (SNR) is achieved. In this paper, a 1st-order PWM signal generator is presented. In order to obtain a much higher precision PWM signal a 2nd-order PWM signal generator is discussed. But the 2nd-order PWM is unstable. Hence, PI compensation is applied to stabilize the modulator. A better PWM signal generator with PI compensation is presented. From the improved generator, a low distortion PWM signal was generated, and the SNR of output signal is increased about 20 dB compared to the 1st-order PWM signal generator.