Patent ID: 8421665

Claim:
An A/D conversion circuit comprising: a pulse transit circuit into which either a power supply or current source is input and a pulse signal is also input, and through which the pulse signal transits; a transit position detection section that detects a transit position of the pulse signal within the pulse transit circuit, and outputs data in accordance with the transit position; and a digital data creation section that, based on the data output by the transit position detection section, creates digital data that corresponds to the size of the power supply or current source, wherein: the pulse transit circuit is formed by a plurality of inverter circuits that are joined together in series in a ring shape; the plurality of inverter circuits are formed by identical logical elements in which delay times between input signals and output signals change in accordance with the size of the power supply or current source; in the pulse transit circuit, a start-up signal that causes the transiting of the pulse signal to commence is input into one of the plurality of inverter circuits; the transit position detection section detects the transit position of the pulse signal within the pulse transit circuit based on the output signals from each one of the plurality of inverter circuits; each of the logical elements have a first input terminal that is input the input signals, a second input terminal, an output terminal that output the output signals, and a power supply terminal that is input the power supply or current source; the second input terminal of one of the logical elements is input the start-up signal; and the second input terminal of the other of the logical elements is input the power supply or a constant power source.