Apparatus for differential interpolation pulse width modulation digital-to-analog conversion and output signal coding method thereof

A pulse-width interpolation method, applicable to an iPWM module having a PWM, an interpolation resolution unit, a self-calibration unit and a differential pulse width generator, comprising the steps of:

• selecting PWM sample rate M to determine number of bits N required;
• selecting a minimum pulse-width TP able to pass through a power driver stage without diminishing;
• determining a minimum time resolution TR;
• determining an number of interpolation resolution bits K for input signal S quantized into an N-bit representation having a 1-bit sign, a J-bit MSB part and a K-bit LSB part, wherein N=J+K,
• K
• =
• log
• 2
• 
• ⌊
• T
• P
• T
• R
• ⌋
• ,
• and TR being the minimum time resolution of the input signal S;
• and
• outputting interpolation pulses DP and DN of designated width.

A single-sided expanded iPWM coding scheme, applicable to representing codes generated by an iPWM module receiving an input signal S and outputting a first pulse and a second pulse, said input signal being a numerical value ranging from −(2N−1) to (2N−1), widths of said first pulse and said second pulse being variable, leading edge of said first pulse and leading edge of said second pulse occurring at the same time, said codes being defined as the difference between said first pulse and said second pulse, said coding scheme comprising:

• a minimum pulse-width TP;
• a minimum time resolution TR;
• for input signal S=0, width of said first pulse=width of said second pulse=TP;
• or
• input signal S=0, width of said first pulse=width of said second pulse=0;
• for input signal S=±1, width of said first pulse=Tp+TR, width of said second pulse=TP;
• for input signal S=±2, width of said first pulse=Tp+2TR, width of said second pulse=TP;
• for other values of input signal S, width of said first pulse=Tp+S*TR, width of said second pulse=TP.

A double-sided expanded iPWM coding scheme, applicable to representing codes generated by an iPWM module receiving an input signal S and outputting a first pulse and a second pulse, said input signal being a numerical value ranging from −(2N−1) to (2N−1), widths of said first pulse and said second pulse being variable, mid-point of said first pulse coinciding mid-point of said second pulse, said codes being defined as the difference between said first pulse and said second pulse, said coding scheme comprising:

• a minimum pulse-width TP;
• a minimum time resolution TR;
• for input signal S=0, width of said first pulse=width of said second pulse=2Tp;
• or
• input signal S=0, width of said first pulse=width of said second pulse=0;
• for input signal S=±1, width of said first pulse=Tp+2TR, width of said second pulse=TP;
• for input signal S=±2, width of said first pulse=Tp+4TR, width of said second pulse=TP;
• for other values of input signal S, width of said first pulse=Tp+2*S*TR, width of said second pulse=TP.