An analog-to-digital (A/D) conversion system includes a track-and-hold circuit, a digital-to-analog (D/A) conversion circuit, a comparison circuit and a control circuit. The track-and-hold circuit is configured to output a first signal based on an input signal. The D/A conversion circuit is configured to generate a second signal based on an N-bit logical signal. The comparison circuit is configured to generate a comparison result based on the first signal and the second signal. The control circuit is configured to generate the N-bit logical signal according to N comparison results from the comparison circuit.