Patent ID: 7872600

Claim:
A low cost analog to digital converter, comprising: a microprocessor, comprising a first output terminal, a second output terminal and an input terminal, wherein the first output terminal thereof is used for providing a pulse modulation signal according to a first digital value, and the input terminal comprises a logic threshold voltage; a low-pass filter, coupled to the first output terminal of the microprocessor, for performing the filtering operation to the pulse modulation signal to output a pulse average voltage; and an analog adder, comprising a first input terminal for receiving the pulse average voltage, a second input terminal for receiving a voltage under test, and an output terminal for providing a composite voltage, wherein the composite voltage comprises the pulse average voltage with a first proportion and the voltage under test with a second proportion, wherein the input terminal of the microprocessor receives the composite voltage, and adjusts the first digital value such that the composite voltage approaches the logic threshold voltage, and then an analog to digital conversion value corresponding to the voltage under test is obtained according to the first digital value, wherein the second output terminal of the microprocessor is used for outputting the analog to digital conversion value, wherein a complementary operation is provided to the first digital value to obtain a analog to digital conversion value corresponding to the voltage under test.