AD CONVERSION SYSTEM

PROBLEM TO BE SOLVED: To provide an AD conversion system capable of suppressing an increase in circuit scale to be minimum even if the number of AD conversion parts increases.SOLUTION: The AD conversion system converts a plurality of analogue signals to a serial digital signal and includes a plurality of AD conversion units which perform AD-conversion with each of a plurality of analogue signals at the same timing, a parallel-serial conversion unit which parallel-serial converts the plurality of digital signals to a serial digital signal for outputting, and a control unit that supplies a control signal to the parallel-serial conversion unit. The parallel-serial conversion unit comprises D flip-flops (D-FF) of (the number of AD conversion units constituting the AD conversion system added with one) connected in series, and includes a shift circuit in which the control signal from the control unit is inputted and a gate circuit of the same number as the AD conversion units. It also includes a parallel-serial conversion circuit which controls the output of a digital signal inputted into each gate circuit according to the output signal of D-FF at each stage, and an AD conversion operation control unit which outputs an operation permission signal of the AD conversion unit based on each output signal of D-FF at the front most stage and that of D-FF at the last stage.