Patent ID: 7844102

Claim:
An analog-to-digital conversion apparatus, comprising: a reference voltage generation circuit for generating a first reference signal having a first constant voltage level and a second reference signal having a second constant voltage level different from the first constant voltage level; an analog-to-digital conversion circuit including a ring-gate-delay circuit having a plurality of inverting circuits that perform an inverting operation at a variable speed depending on a power voltage of the ring-gate-delay circuit and are connected in a ring pattern, the analog-to-digital conversion circuit converting a physical quantity signal having a voltage level varying with an amount of a physical quantity, the first reference signal, and the second reference signal, each signal being provided to the ring-gate-delay circuit as the power voltage, to a physical quantity data, a first reference data, and a second reference data, respectively, based on the number of times a pulse signal input to the ring-gate-delay circuit circulates through the ring-gate-delay circuit; and a signal processing means for calculating an output value corresponding to the physical quantity based on a ratio between a first deference and a second difference, wherein the first difference is a difference between any single pair from the physical quantity data, the first reference data, and the second reference data, and the second difference is a difference between one of other pairs from the physical quantity data, the first reference data, and the second reference data.