Low-cost, protected capacitive sensing circuit for loading mode operation of capacitive sensors employing heater members

US12132478B2 · kind B2 · utility

Assignee

• IEE INTERNATIONAL ELECTRONICS & ENGINEERING S.A. · LU

Inventors

• Laurent Lamesch · Reichlange, LU
• Tobias JUSTINGER · Hermeskeil, DE
• Michael Puetz · Trier, DE
• Thomas Faber · Schweich, DE
• Christoph Wendt · Mettendorf, DE
• Johnny LORANG · Grentzingen, LU

Key dates

• Filing date: Apr 8, 2022
• Grant date: Oct 29, 2024
• Expiry date: Apr 8, 2042

Classification

• Technology area (CPC H): Electricity
• CPC primary: H03K2217/960745
• WIPO field: Transport
• WIPO sector: Mechanical engineering

Abstract

An impedance measurement circuit for determining a complex impedance of a capacitive sensor that is configured for employing at least one electric heater member as an electrode to be operated in loading mode. The measurement circuit includes: a signal generating unit for providing an electric measurement signal; a signal sensing circuit measuring current through the at least one electric heater member; an electric heater member connection circuit comprising a plurality of MOSFETs for selectively electrically connecting the electric heater member either to the signal sensing circuit for complex impedance measurement or to a DC electric power unit for heating purposes; and a control and evaluation unit that is configured for controlling a switching status of the plurality of MOSFETs according to a predefined sequence, and for determining a complex impedance from the determined currents with reference to a complex reference potential during predefined stages of the predefined sequence.