Patent ID: 8593315

Claim:
An A/D conversion device, comprising: a sample-and-hold unit that samples an analog value of an analog input signal and holds the analog value for a predetermined period of time; an A/D conversion unit that converts an analog input voltage from the sample-and-hold unit into a digital output; a reference voltage generation unit that applies one of a first reference voltage and a second reference voltage to the A/D conversion unit in a switching manner; and a digital processing unit having a function of reading the digital output, determining a control value for correcting the digital output, and outputting the control value to the A/D conversion unit, wherein the A/D conversion unit performs an operation of converting an analog value into a digital value twice during a hold period of the analog value, and, in a first conversion operation, the A/D conversion unit compares the analog value with the first reference voltage and outputs a comparison result as first converted data, and in a second conversion operation, the A/D conversion unit compares the analog value with the second reference voltage and outputs a comparison result as second converted data, wherein the second reference voltage is set to a voltage obtained by adding or subtracting a minimum resolution voltage to or from the first reference voltage, and wherein the digital processing unit averages errors of the first and second converted data by digital processing to detect an A/D conversion error, feeds back a detection result to the A/D conversion unit as the control value to perform voltage control, and repeats the operation to reduce the conversion error.