A/d conversion device

An A/D conversion device which converts an analog input voltage to a digital value, the A/D conversion device comprising:

• a first pulse delay circuit which receives a first pulse signal at a first time as input, and has multiple stages of delay units which are connected together and delay the first pulse signal for a delay period according to a magnitude of a first analog voltage;
• a first pulse passage stage detection circuit which detects a first number of stages when the first pulse signal has passed through the delay unit in the first pulse delay circuit;
• a second pulse delay circuit which receives a second pulse signal at a second time that is the same as the first time, and has multiple stages of delay units which are connected together and delay the second pulse signal for a delay period according to a magnitude of a second analog voltage different from the first analog voltage;
• a second pulse passage stage detection circuit which detects a second number of stages when the second pulse signal has passed through a delay unit in the second pulse delay circuit;
• a time output circuit which outputs a time signal indicating a time at which a difference between the first number of stages and the second number of stages becomes a predetermined number of stages;
• a third pulse delay circuit which receives a third pulse signal at a third time as input, at a same time as the first time and the second time as input, and has delay units which are connected together and delay the third pulse signal for a delay period according to a magnitude of the analog input voltage;
• a third pulse passage stage detection circuit which detects a third number of stages when the third pulse signal has passed through a delay unit in the third pulse delay circuit;
• and
• an output circuit which outputs the digital value corresponding to the third number of stages detected at a time indicated by the time signal.