Patent ID: 7782243

Claim:
A direct capacitance-to-digital converter, for sensing a stray capacitor related to a to-be-measured capacitor, and directly converting an inductive capacitance of said to-be-measured capacitor into a digital signal, a first end of said stray capacitor being connected to a first end of said to-be-measured capacitor, a second end of said stray capacitor being grounded, said direct capacitance-to-digital converter comprising: a first integrator, for receiving an input signal at second end of said to-be-measured capacitor, after integration, generating a first-stage integrator output signal; a second-stage integrator, for receiving said first-stage integrator output signal, after integration, generating a second-stage integrator output signal, said second-stage integrator further comprising an integral capacitor and an integral amplifier, one end of said integral capacitor and an inverted input end of said integral amplifier being connected to input signal of said second-stage integrator, a non-inverted input end of said integral amplifier being grounded, the other end of said integral capacitor and an output end of said integral amplifier being connected to said second-stage integrator output signal; a comparator, for receiving said second-stage integrator output signal, after comparing with a standard voltage, generating said digital signal; and a trigger unit, for generating a plurality of control signals to control first end and second end of said to-be-measured capacitor and said first-stage integrator, said control signals comprising a first switch signal, a second switch signal, a third switch signal, a third inverted switch signal, a fourth switch signal and a fifth switch, said third inverted switch signal being the inverted phase of said third switch signal, high level of said first switch signal not overlapping high level of said fifth switch signal; where said trigger unit sequentially generating high level of said first switch signal, said second switch signal and said third switch signal for sensing voltage of said stray capacitor, and said trigger unit sequentially generating high level of said fourth switch signal and said fifth switch signal for sensing voltage of said to-be-measured capacitor.