Touch detection circuit with different charging and discharging currents and operating method thereof
AssigneePixart Imaging Inc.
InventorSung-Han Wu
Life of this patent
Estimating the term…
Abstract
There is provided a touch detection circuit including a charging circuit, a discharging circuit, a counter and a processor. The charging circuit charges a detection capacitor within a charging interval using different currents. The discharging circuit discharges the detection capacitor within a discharging interval using different currents. The counter counts the charging interval and the discharging interval. The processor subtracts a baseline time from a counted charging time and a counted discharging time to cancel the noise interference.
Claims19
A touch detection circuit, comprising:
- a detection capacitor, configured to generate a capacitor voltage;
- a charging circuit, configured to charge the detection capacitor within a first charging interval using a first charging current, and charge the detection capacitor within a second charging interval using a second charging current smaller than the first charging current;
- a discharging circuit, configured to discharge the detection capacitor within a first discharging interval using a first discharging current, and discharge the detection capacitor within a second discharging interval using a second discharging current smaller than the first discharging current;
- a counter, configured to sequentially count the first charging interval, the second charging interval, the first discharging interval and the second discharging interval as a detection cycle;
- and
- a processor, configured to identify a touch event according to the second charging interval and the second discharging interval without according to the first charging interval and the first discharging interval.
A capacitive switch, comprising:
- a detection capacitor, configured to generate a capacitor voltage;
- a charging circuit, configured to charge the detection capacitor sequentially using a first charging current and a second charging current, smaller than the first charging current, within a charging interval;
- a discharging circuit, configured to discharge the detection capacitor sequentially using a first discharging current and a second discharging current, smaller than the first discharging current, within a discharging interval;
- a counter, configured to sequentially count the charging interval and the discharging interval as a detection cycle;
- and
- a processor, configured to subtract a charging reference time and a discharging reference time from the detection cycle to generate a time of interest, and output a control signal according to a variation of the time of interest between successive detection cycles.
An operating method of a touch detection circuit, the touch detection circuit comprising a detection capacitor, a charging circuit, a discharging circuit and a counter, the operating method comprising:
- charging, using the charging circuit, the detection capacitor using a first charging current, and counting a first charging interval using the counter;
- charging, using the charging circuit, the detection capacitor using a second charging current, smaller than the first charging current, and counting a second charging interval using the counter;
- discharging, using the discharging circuit, the detection capacitor using a first discharging current, and counting a first discharging interval using the counter;
- discharging, using the discharging circuit, the detection capacitor using a second discharging current, smaller than the first discharging current, and counting a second discharging interval using the counter;
- and
- identifying a touch event according to a time variation of multiple summations of the second charging interval and the second discharging interval.
Dependencies are inferred from the claim text.