Drive circuit and drive method for a gas sensor
AssigneeSiemens Aktiengesellschaft
InventorTim Walde
Life of this patent
Estimating the term…
Abstract
A method and device for driving a gas sensor includes a three point circuit determining a temperature of a gas sensor having a resistive heating element by determining a measuring current with a measuring resistor flowing through the resistor in a measuring phase. The three-point measurement makes it possible to determine accurately the line resistance of an incoming line branch, which can also be used approximately for the line resistance of another incoming line branch. Naturally, the tap may also be provided on the incoming line side.
Claims15
A drive circuit for a gas sensor having a resistive heating element with an incoming line branch and an outgoing line branch connected to a reference potential, comprising:
- a feed voltage source producing a feed voltage;
- a supply branch having said feed voltage applied thereto;
- a first controllable switching element connected to said supply branch and to the incoming line branch of the heating element;
- a measuring voltage source;
- a second controllable switching element connected to said measuring voltage source;
- a measuring resistor having:
- a first side with a first potential, said first side connected to said second switching element;
- and
- a second side with a second potential, said second side connected to said supply branch;
- a current heating path flowing, when said first switching element is turned on, from said supply branch through said first switching element, the incoming line branch of the heating element, the heating element, and the outgoing line branch to the reference potential;
- and
- a measuring current path leading from said measuring voltage source through said second switching element and said measuring resistor into said supply branch, said measuring current path being closed when said first switching element is turned off and said second switching element is turned on;
- and
- a measuring device having:
- a first measuring pin connected to said first side of said measuring resistor for tapping off said first potential;
- a second measuring pin connected to said second side of said measuring resistor for tapping off said second potential;
- and
- a third measuring pin connected to the outgoing line branch of the heating element for tapping off a potential at the outgoing line branch.
In a circuit for a gas sensor with a resistive heating element having an incoming line branch and an outgoing line branch connected to a reference potential, a gas sensor drive circuit, comprising:
- a feed voltage source producing a feed voltage;
- a supply branch having said feed voltage applied thereto;
- a first controllable switching element connected to said supply branch and to the incoming line branch of the heating element;
- a measuring voltage source;
- a second controllable switching element connected to said measuring voltage source;
- a measuring resistor having:
- a first side with a first potential, said first side connected to said second switching element;
- and
- a second side with a second potential, said second side connected to said supply branch;
- a current heating path flowing, when said first switching element is turned on, from said supply branch through said first switching element, the incoming line branch of the heating element, the heating element, and the outgoing line branch to the reference potential;
- and
- a measuring current path leading from said measuring voltage source through said second switching element and said measuring resistor into said supply branch, said measuring current path being closed when said first switching element is turned off and said second switching element is turned on;
- and
- a measuring device having:
- a first measuring pin connected to said first side of said measuring resistor for tapping off said first potential;
- a second measuring pin connected to said second side of said measuring resistor for tapping off said second potential;
- and
- a third measuring pin connected to the outgoing line branch of the heating element for tapping off a potential at the outgoing line branch.
A method for driving a gas sensor having a resistive heating element, which comprises:
- a) during heating phases, applying a heating current flowing in a heating current circuit to the heating element;
- b) during in measuring phases, applying a measuring current smaller than the heating current and flowing in a measuring current circuit to the heating element by a given measuring voltage, the measuring current circuit and the heating current circuit being formed in given sections by same conductors;
- c) determining a resistance of the heating element from the measuring current and the measuring voltage;
- d) alternating the measuring phases and the heating phases, deriving the temperature from the resistance of the heating element, and taking the derived temperature into account during a configuration of the heating phases;
- and
- e) measuring a voltage drop during the measuring phase in at least a part of the given sections, ascertaining therefrom a corresponding line resistance, and taking the line resistance into account when determining the resistance of the heating element.
Dependencies are inferred from the claim text.