Patent ID: 9587964
Date: 2017-03-07
CPC Classifications: G01D,G01R,G05B,G06F,H03K,H03M

Claim:
1. A proximity detection system, said system comprising: a comparator having first and second inputs and an output, wherein the second input is coupled with a reference voltage and the first input is coupled with a holding capacitor; a capacitive sensor; a switch for coupling the capacitive sensor alternately to a voltage and the holding capacitor; a clock having an output; a flip-flop having an input coupled with the output of the comparator, a clock input coupled to the output of the clock and an output; a feedback resistor coupled between the output of the flip-flop and the first input of the comparator; a duty cycle counter having a clock input coupled to the output of the clock, a reset input, an enable input coupled to the output of the flip-flop, and an output for providing a number of clock outputs counted, wherein the duty cycle counter only counts the clock outputs when the enable input thereof is at a first logic level; and a circuit for controlling the switch whenever the output of the flip-flop goes from a second logic level to the first logic level; wherein the number of clock outputs counted are used in determining proximity of an object to the capacitive sensor.