An analog-to-digital conversion system includes an analog-to-digital converter and a power supply. The analog-to-digital converter is configured to convert an analog input signal to generate a digital output signal, and configured to generate a control signal according to a state of converting the analog input signal. The power supply is configured to provide a supply voltage to the analog-to-digital converter, and change the ability to provide the supply current of the power supply according to the control signal to stabilize the supply voltage.