US 12,250,520 B2
Capacitive sensor assembly and electrical circuit therefor
Shenjie Wang, Olten (CH); René Scheuner, Gutenswil (CH); and Mark Niederberger, Einsiedeln (CH)
Assigned to Knowles Electronics, LLC, Itasca, IL (US)
Filed by Knowles Electronics, LLC, Itasca, IL (US)
Filed on Dec. 31, 2022, as Appl. No. 18/092,285.
Prior Publication US 2024/0223965 A1, Jul. 4, 2024
Int. Cl. H04R 19/04 (2006.01); H03F 3/45 (2006.01); H04R 1/04 (2006.01)
CPC H04R 19/04 (2013.01) [H03F 3/45475 (2013.01); H04R 1/04 (2013.01); H03F 2200/165 (2013.01); H04R 2201/003 (2013.01)] 20 Claims
OG exemplary drawing
 
1. An electrical circuit for a capacitive sensor assembly, the electrical circuit comprising:
a capacitive motor interface having an input resistance greater than 100 T ohms, the capacitive motor interface connectable to a capacitive motor;
a charge pump circuit comprising an output (VCP) and reference signal input that controls a voltage on the output;
a low pass filter comprising diode-based resistive element (VDZ) coupled between the charge pump circuit output (VCP) and a filter capacitor, a bias voltage node (Vbias) between the diode-based resistive element (VDZ) and the filter capacitor, the bias voltage node (Vbias) coupled to the capacitive motor interface;
a frontend amplifier circuit having an input coupled to the capacitive motor interface and an output coupled to an output of the electrical circuit;
an injection current source (ICS) coupled to the charge pump circuit output (VCP) and configured to control voltage across the diode-based resistive element (VDZ) during a transient startup phase of the charge pump circuit.