Supply voltage generation for resistive sensor elements

Abstract

A circuit arrangement for operating a resistive sensor element is described. According to one embodiment, the circuit arrangement comprises a first supply connection and a second supply connection and a sensor circuit having at least one resistive sensor element, a supply voltage being added between the first supply connection and the second supply connection during operation. The sensor circuit has a first circuit node and a second circuit node for applying a sensor voltage, wherein the first circuit node is connected to the first supply connection. The circuit arrangement further comprises a sensor power supply circuit designed to electrically couple the charged capacitor with the second circuit node during the measurement time interval such that the sensor voltage between the first circuit node and the second circuit node is greater than the supply voltage.

Description

Technical Field

[0001] This specification relates to the field of sensor technology, in particular to the generation of a supply voltage for one or more resistive sensor elements. Background Art

[0002] There are many sensors with resistive sensor elements whose resistance directly or indirectly depends on the physical quantity to be measured. An example of this is a TC sensor (thermal conductivity sensor) for measuring the thermal conductivity of a gas. In a sensor of this type, a resistor (sensor element) is heated by applying a voltage. The resistor is exposed to the analysis gas. Since a voltage is applied to the sensor element, a sensor current flows, which results in a certain power loss in the sensor element. Due to the power loss, the sensor element (e.g., the resistor) heats up to a specific temperature above the ambient temperature. At this temperature, the total thermal loss of the resistor is equivalent to the consumed electrical energy. The thermal loss depends to a large extent on the thermal conductivity of the analysis gas. The higher the thermal conductivity of the gas, the higher the cooling effect, and the lower the temperature (and the greater the conductivity) of the sensor element under constant voltage. The greater the conductivity of the resistance of the sensor element, the greater the current. Therefore, the current is a measure of the thermal conductivity of the analysis gas.

[0003] The sensitivity of such a TC sensor increases with the supply voltage. The output signal of the sensor has an approximately cubic relationship with the applied supply voltage. The supply voltage of the sensor is not applied continuously, but at regular intervals (periodically or from time to time) to reduce the average power consumption and extend the service life of the sensor.

[0004] In many applications, the operation of the sensor is controlled by means of an integrated control circuit, for example by means of a microcontroller. Like many other integrated circuits, such a control circuit can be operated at a relatively low supply voltage, for example at 3.3 volts. However, for resistive sensor elements, especially for the above-mentioned TC sensors, this voltage may be too low to achieve sufficient sensor sensitivity.

[0005] The task set by the inventors is to improve the existing concepts for the operation of resistive sensor elements, in particular with regard to the generation of the sensor supply voltage. Summary of the Invention

[0006] The above object is achieved by a method according to the invention. Various embodiments and further improvements are as follows.

[0007] The following describes a circuit arrangement for operating a resistive sensor element. According to one embodiment, the circuit arrangement includes a first power supply connection and a second power supply connection, and a sensor circuit having at least one resistive sensor element, with a supply voltage present between the first power supply connection and the second power supply connection during operation. The sensor circuit has a first circuit node and a second circuit node for applying a sensor voltage, wherein the first circuit node is connected to the first power supply connection. The circuit arrangement further includes a sensor power supply circuit that is designed to electrically couple a charged capacitor to the second circuit node during a measurement time interval such that the sensor voltage between the first circuit node and the second circuit node is greater than the supply voltage.

[0008] Furthermore, a method for operating a sensor circuit having at least one resistive sensor element is described, wherein the sensor circuit has a first circuit node and a second circuit node for applying a sensor voltage. According to one embodiment, the method includes charging a capacitor, which is achieved by coupling the capacitor to a voltage source that provides a supply voltage between a first power supply connection and a second power supply connection, wherein the first circuit node of the sensor circuit is connected to the first power supply connection. The method further includes coupling the charged capacitor to the second circuit node of the sensor circuit during a measurement time interval such that the resulting sensor voltage between the first circuit node and the second circuit node of the sensor circuit is greater than the supply voltage. Description of the Drawings

[0009] The embodiments are explained in more detail below with reference to the drawings. The drawings are not necessarily to scale, and the embodiments are not limited to the aspects shown. Instead, the emphasis is on presenting the principles underlying the embodiments. Regarding the drawings:

[0010] Figure 1 The construction of the sensor element of the TC sensor is illustrated by means of a micromechanical structure.

[0011] Figure 2 A bridge circuit (resistive bridge) that can be used in the TC sensor is shown.

[0012] Figure 3 is a graph illustrating the dependence of the sensor sensitivity on the sensor voltage.

[0013] Figure 4 A circuit arrangement with a power supply circuit for generating a sensor voltage for a sensor having a resistive sensor element is shown as a first embodiment.

[0014] Figure 5 contains a plurality of timing diagrams for illustrating Figure 4 the function of the circuit arrangement.

[0015] Figure 6 is shown in more detailFigure 4 Another embodiment of the power supply circuit.

[0016] Figure 7 Shows Figure 4 An alternative (equivalent) implementation of the example of

[0017] Figure 8 And Figure 9 Shows Figure 4 An extension / modification of the example of , where in addition to the bridge output voltage, the sensor voltage across the bridge is also measured.

[0018] Figure 10 Is a diagram illustrating the measurement process. Detailed implementation

[0019] Figure 1 Shows the micromechanical structure of the resistive sensor element of the TC sensor. The micromechanical structure can be integrated in a silicon chip, which is in turn arranged in a chip housing (package). Various methods for manufacturing integrated microelectromechanical systems (MEMS) are known per se and will not be discussed further here.

[0020] According to Figure 1 The example shown, the micromechanical structure 10 forms a frame that can have, for example, a rectangular shape. However, the shape of the frame is not necessary. The electrical conductor 20 extends transversely across the frame (similar to a "bridge" from one side of the frame to the opposite side), which can be designed, for example, as a strip conductor. The conductor 20 can be made of metal (such as aluminum) or polysilicon. In the case of a metal conductor, it can be arranged on a silicon bridge tab connecting two opposite sides of the frame 10.

[0021] The micromechanical structure 10 forms a cavity in which the above-mentioned analysis gas can be located. In practice, the analysis gas is usually a mixture of several gaseous substances, such as air. Figure 1 Also shown in S is a voltage source Q S that generates a sensor voltage V S . The resulting sensor current i S depends on the resistance R S of the sensor element (conductivity σ S -1 = R S ). The power P S 2 converted into heat in the sensor element is equal to V S ·σ S 2 = i S ·R S . In thermal equilibrium (i.e., when the temperature of the conductor 20 is constant), the heat carried away per unit time (cooling power) is equal to the electrical power V2 ·σ S The greater the thermal conductivity κ of the analysis gas, the better the cooling performance. Therefore, the greater the thermal conductivity κ of the analysis gas, the lower the temperature T of the conductor 20 S . However, the lower temperature T of the conductor 20 S results in a greater conductivity σ S (because the temperature coefficient of the resistance R S is positive), that is, σ S = σ S (κ) is a function of the thermal conductivity κ. The sensor current i S also depends on the thermal conductivity κ because i S = V S ·σ S (κ). A higher thermal conductivity κ causes a lower temperature T S , thus causing a higher conductivity σ S and a higher sensor current i S .

[0022] As with many other resistive sensors, the resistive sensor elements according to Figure 1 can be connected to form a bridge circuit (also known as a Wheatstone bridge). Figure 2 An example is shown. Thus, the bridge circuit includes two voltage dividers that are connected between a first bridge power node (across which a supply voltage V SUPPLY ) and a second bridge power node (across which, for example, a reference or ground potential V REF ) is applied. Two of the four bridge resistors are sensor elements according to Figure 1 and are labeled R S1 and R S2 . The other two resistors are reference resistors R REF1 and R REF2 . Assuming R REF1 = R REF2 = R and R S1 = R S2 = R + ΔR and the approximate relationship 2R + ΔR ≈ 2R (since ΔR << R), the bridge output voltage V OUT = (V SUPPLY - V REF )·ΔR / 2, where ΔR represents the deviation of the sensor resistance from the known nominal resistance value R. In many known sensor circuits, the reference potential V REF is equal to the ground potential, i.e., 0 volts.

[0023] Figure 3 The graph of OUT illustrates the dependence of the bridge output voltage V SUPPLY on the bridge supply voltage V REF= 0 V). The two curves shown relate to different gas mixtures, labeled "Gas A" and "Gas B" respectively. It can be seen that the bridge output voltage V OUT increases disproportionately excessively with respect to the bridge supply voltage V SUPPLY because when the bridge supply voltage V SUPPLY is higher, the current flowing through the sensor element and its temperature T S also increase. When the voltage V SUPPLY increases by two-thirds (e.g., from 3 V to approximately 5 V with an increase of about 67%), the bridge output voltage V OUT increases significantly more than 67%, increasing by several hundred percent in the example shown.

[0024] In addition to the sensor element, the sensor generally also includes circuitry for manipulating the sensor element and for (post-)processing the sensor signal (e.g., the bridge output voltage V OUT ). These tasks can be performed by a control circuit, which can include, for example, a microcontroller. The control circuit (microcontroller) can, for example, have an analog-to-digital converter, which is designed to digitize the output voltage of the sensor element or the bridge output voltage V Figure 2 of the resistance bridge (see OUT ). Modern digital circuitry (such as microcontrollers) operates at a relatively low supply voltage (e.g., 3.3 volts). However, as explained above with reference to Figure 3 , a higher supply voltage is advantageous for resistive sensors (where the sensor element is arranged in, for example, a resistance bridge) and especially for TC sensors.

[0025] For these reasons, in known sensor concepts two different supply voltages are required, where, for example, the 3.3 V supply voltage for the microcontroller is generated from a 6 V supply voltage applied to the resistance bridge by means of a linear voltage regulator, which results in undesirable losses in the voltage regulator. In addition to the voltage regulator, a DC / DC switching converter can also be used, for example, to generate a 3.3 V supply voltage from a 6 V supply voltage and vice versa. However, DC / DC switching converters such as boost converters or buck converters are complex and require inductors that cannot be integrated into the chip.

[0026] Figure 4 The circuit arrangement shown includes a resistance bridge 30, a control circuit 40 (microcontroller) having an analog-to-digital converter for digitizing the bridge output voltage V OUT , and a supply circuit, which is designed to temporarily (during the measurement time interval) supply the bridge circuit 30 with a supply voltage V SUPPLY -V REF , which is greater than the supply voltage V SUPPLY also supplied to the control circuit 40.

[0027] In Figure 4 the example shown, the supply voltage is 3 volts (V SUPPLY = 3V). The supply voltage V SUPPLY is supplied to the control circuit 40 and the first bridge power node N 1 . The second bridge supply node N 2 is at a reference voltage V N2 = V REF , which is not constant in the example described herein but is provided by the power supply circuit 50. The operation of the power supply circuit is controlled by the control circuit 40 (microcontroller), where the control circuit 40 is designed to temporarily (during the measurement time interval) apply a voltage V 2 to the bridge supply node N N2 , and this voltage V N2 is lower than the operating voltage range 0 - 3V. That is, the voltage V N2 is negative during the measurement time interval, so the bridge supply voltage V SUPPLY - V N2 is greater than the supply voltage V SUPPLY . The function of the power supply circuit 50 is explained in more detail below using Figure 5 the timing diagram.

[0028] The power supply circuit 50 receives a logic signal V IO generated by the microcontroller 40 as a control signal. Common microcontrollers have digital outputs that can output logic signals. Some microcontrollers have configurable connectors (so-called general-purpose IO (GPIO) terminals) that can be configured not only as digital inputs but also weighted as digital outputs. Such GPIO connectors can also be used to output the logic signal V IO . The logic signal V IO can only assume two different levels, namely: a low level, approximately corresponding to the ground potential V GND = 0V; and a high level, approximately corresponding to the supply voltage V SUPPLY . In the example shown, the power supply circuit 50 has a capacitor C 1 , which is connected on the one hand to the digital output of the microcontroller 40 (e.g., via a resistor R 1 for current limiting) and on the other hand to the circuit node N 3 . This node N 3 can in turn be connected to the ground node GND via a diode D 1 , where the diode D 1 can also be replaced by another component such as a controllable electronic switch (e.g., a transistor or a more complex network). The node N 3 is connected to the second bridge supply node N 1(which is a MOS transistor in the illustrated example) is connected to the second bridge supply node N 2 The transistor T 1 can also be replaced by other types of electronic switches or more complex switching networks.

[0029] The microcontroller can display the measured time interval by the level of the logic signal V IO . As shown in the example of the chart (a) of Figure 5 , the measured time interval (from time t 1 to time t 2 ) is defined by the low level (about 0V) of the logic signal V IO . Outside the measured time interval, the logic signal has a high level (about 3V in the illustrated example). As long as the logic signal V IO is at a high level, the current i C will flow from the digital output GPIO of the microcontroller 40 through the resistor R 1 , the capacitor C 1 and the diode D 1 to the ground node GND and charge the capacitor C 1 . When the capacitor voltage V C reaches a steady value, the charging process ends, and this steady value substantially corresponds to the high level of the logic signal minus the forward voltage V 1 of the diode D F (about 0.7V) (i.e., V C ≈ V SUPPLY - V F ). Immediately before time t 1 , the capacitor voltage V C is actually constant, and the voltage V N3 is approximately equal to the voltage drop V 1 across the diode D F (V N3 = V F ≈ 0.7V, see the chart (b) of Figure 5 ). If the microcontroller 40 sets the level of the logic signal V 1 (i.e., at the start of the measured time interval) from high to low at time t IO , the voltage V 3 of the node N N3 suddenly drops from V F to a negative value of approximately -V SUPPLY + V F (i.e., about -2.3 volts in the current example) and the diode D 1 is cut off. At the same time (also at time t 1 ), the electronic switch / transistor T 1 conducts and connects the node N 3 to the bridge supply node N2 is connected, resulting in a voltage V appearing at the bridge circuit 30 SUPPLY -V N3 , which is greater than the supply voltage V SUPPLY (initially approximately 2·V SUPPLY -V F ). For simplicity, the voltage drop across the transistor T 1 is ignored.

[0030] During the measurement time interval (between t 1 and t 2 ), a current flows through the resistance bridge 30 while the capacitor C 1 discharges. As a result, the voltage V N3 increases during the measurement time interval, and the bridge supply voltage V SUPPLY -V N3 decreases accordingly (see the graph (c) in Figure 5 ). Depending on the capacitance of the capacitor C 1 , the voltage change ΔV during the measurement time interval can be smaller or larger. At the end of the measurement time interval (at time t 2 ), the microcontroller 40 sets the level of the logic signal V IO from low to high, and the capacitor is recharged relatively quickly (not shown in detail in Figure 5 ). The diode D 1 conducts again, the electronic switch (transistor T 1 ) turns off, and the voltage V SUPPLY -V N2 across the bridge circuit 30 drops to zero. During the measurement time interval, the microcontroller 40 can sample and digitize the trend of the bridge output voltage V OUT (also see Figure 10 ). The microcontroller 40 can determine the sought information from the corresponding digital values (for example, analyze the thermal conductivity of a gas in the case of a TC sensor). For this purpose, the microcontroller can use calibration data and / or characteristic curves stored in the memory.

[0031] Figure 4 The circuit shown in is only an example. In general, the embodiments described herein relate to circuit arrangements for operating sensors. In a general example, the circuit arrangement is supplied by a supply voltage V SUPPLY . For this purpose, the circuit arrangement has a first supply connection and a second supply connection GND, and a supply voltage V SUPPLY exists between the first supply connection and the second supply connection during operation. The circuit arrangement also has a sensor circuit 30, which has at least one resistive sensor element (see Figure 2 , resistance R S1 , R S2)。The sensor voltage V S is supplied to the sensor circuit 30 (e.g., a Wheatstone bridge). Thus, the sensor circuit 30 has a first circuit node N 1 and a second circuit node N 2 , and during measurement (during the measurement time interval), there is a sensor voltage V 1 between the first circuit node N 2 and the second circuit node N S . The first circuit node N 1 of the sensor circuit is connected to the first power supply connector (see Figure 4 ). The circuit device further includes a sensor power supply circuit 50. It is designed to electrically couple a pre-charged capacitor C 1 to the second circuit node N 2 during measurement (during the measurement time interval) (in the illustrated example by means of a transistor T 1 ), such that the sensor voltage V S (which exists between the first circuit node N 1 and the second circuit node N 2 ) is greater than the supply voltage V SUPPLY . That is, the capacitor voltage V 1 of the charged capacitor C C is superimposed on (added to) the supply voltage V SUPPLY . Thus, the sensor voltage V S is (at least temporarily) approximately equal to V SUPPLY + V C .

[0032] Figure 6 shows another example of the power supply circuit 50 and also shows in more detail the operating principle of the digital output GPIO of the microcontroller. As Figure 6 shown, the microcontroller 40 includes a driver that outputs a logic signal V IO at the digital output GPIO. In the illustrated example, the driver includes two electronic switches: a high-side switch and a low-side switch. The high-side switch couples the output GPIO (e.g., the output pin of the microcontroller 40) to the supply voltage V SUPPLY , and the low-side switch couples the output GPIO to the ground potential V GND at the second power supply node GND. The high-side switch is controlled by a Boolean signal CTL, and the low-side switch is controlled by the inverted signal . In fact, the output stage of the driver can be implemented as, for example, a CMOS inverter. The signal CTL can be characterized, for example, by one bit of a register, and the processor of the microcontroller 40 can set (to "1") and reset (to "0") the register. That is, the signal V IO has approximately the value corresponding to V SUPPLYhigh level, or approximately corresponding to V GND low level.

[0033] Figure 6 An example of Figure 4 the power supply circuit 50, where the diode D 1 is replaced by the second transistor T 2 , and its control electrode (gate) is also connected to the digital output GIPO. The control electrode of the transistor T 1 is connected to the ground node GND. If no measurement occurs, the microcontroller 40 outputs a high level as the logic signal V IO . Therefore, the transistor T 2 conducts and the transistor T 1 turns off (because the gate-source voltage is approximately zero). Therefore, the voltage drop across the series circuit R 1 -C 1 is approximately equal to the high level of the signal V IO (i.e., V IO ≈V SUPPLY ), and the capacitor C 1 is charged until the capacitor voltage V C equals the high level of the logic signal V IO (i.e., V C ≈V IO ≈V SUPPLY ). The resistor R 1 is optional and is only used to limit the current.

[0034] During the measurement (within the measurement time interval), the microcontroller 40 outputs a low level (approximately V GND = 0V) as the logic signal V IO . As a result, the transistor T 2 turns off and the potential in the node N 3 decreases from approximately 0V to approximately V N3 = -V C . In the Figure 4 example, the diode D 1 is cut off due to the negative potential in the node N 3 . The negative potential V 3 in the node N N3 also causes the transistor T 1 to conduct (positive gate-source voltage at T 1 ), so the second circuit node N 2 of the sensor circuit 30 (bridge circuit) also has a potential V N2 = V N3 = -V C , which makes the sensor voltage V S across the resistance bridge 30 approximately correspond to the sum V SUPPLY+V C (V S =V SUPPLY -V N2 =V SUPPLY -(-V C )=V SUPPLY +V C )。During the measurement, the sensor voltage V S is greater than the supply voltage V SUPPLY , as explained at the beginning (see Figure 3 ), which can result in higher sensitivity. During the measurement, the capacitor C 1 discharges and the capacitor voltage V C drops. As shown in the graph (c) of Figure 5 , the sensor voltage V S (bridge voltage) is not constant during the measurement.

[0035] Figure 7 shows an alternative (but functionally equivalent) implementation of the example in Figure 4 . It can also be said that the circuit of Figure 7 is complementary to the circuit of Figure 4 . It can be said that the sensor circuit 30 and the power supply circuit 50 are inverted, where the polarity of the diodes changes, the logic signals are inverted, and the n-channel transistors are replaced by p-channel transistors (and vice versa). The function of the circuit device remains unchanged. To charge the capacitor C 1 , the logic signal V IO now has a low level. Thus, the diode D 1 conducts and the (p-channel) transistor T 1 turns off, and current can flow from the voltage source through the capacitor C 1 , the resistor R 1 to the digital output GPIO, thereby charging the capacitor. To perform the measurement, the microcontroller 40 outputs a high level as the logic signal V IO . As a result, the potential V 3 in the node N N3 increases above the supply voltage V SUPPLY (V N3 =V SUPPLY +V C ). Consequently, the diode D 1 cuts off and the transistor T 1 conducts, so the potential V 2 in the node N N2 also increases (V N2 ≈V N3 =V SUPPLY +V C ). The resistance bridge 30 "sees" a sensor voltage V greater than the supply voltage V SUPPLY ​S = V N2 - VN 1 = V N2 (similar to Figure 4 and 6 example).

[0036] Figure 8 and Figure 9 show an Figure 4 expansion / modification of the example in OUT where in addition to the bridge output voltage V S . In Figure 8 the example shown, a voltage divider containing resistors R A and R B is connected in parallel with the sensor element 30 (Wheatstone bridge). The voltage across resistor R A is equal to V S ·R A / (R A + R B ). If the two resistors are the same (R A = R B ), then the voltage across resistor R A is V S / 2. This voltage can be supplied to a differential amplifier 32 (e.g., with a gain of 1), and the output signal of amplifier 32 can be supplied to the analog input of an analog-to-digital converter included in a microcontroller 40, which digitizes (samples and quantizes) the voltage V S ·R A / (R A + R B ). The corresponding digital value represents the sensor voltage V S during the measurement time interval. In other respects, Figure 8 the example is the same as the example in Figure 4 and refers to the relevant description above.

[0037] Figure 9 the example is very similar to the example in Figure 7 but uses a part of the resistance bridge instead of the voltage divider (resistors R A and R B ). Assuming R S1 = R + ΔR and R REF1 = R and the approximation ΔR / R << 1 (ΔR is small enough compared to R to be negligible), when the voltage across resistor R S1 is supplied to amplifier 32, the differential amplifier 32 "sees" half of the sensor voltage as in the example in Figure 7 (see Figure 7 and in combination with Figure 2)。In other respects, Figure 9 The example of Figure 8 is the same as the example of

[0038] Figure 10 The measurement time interval is shown in a time sequence diagram (similar to Figure 5 ). The upper figure shows the sensor voltage V S (in the example of Figure 4 V S = V SUPPLY - V N2 ), and the lower figure shows the corresponding bridge output voltage V OUT and the corresponding digital value (sample) generated by the control circuit 40 (such as a microcontroller) with the help of an analog-to-digital converter. Since the capacitor C 1 (for example, see Figure 4 or Figure 7 ) discharges during the measurement (lasting 10 ms in the example of Figure 10 ), the sensor voltage V S and the bridge output voltage V OUT are not constant. During one measurement time interval (measurement period), a large number of individual measurement values V S are obtained for different sensor voltages V OUT . The microcontroller 40 can determine the information sought from the (digitized) measurement values (for example, in the case of a TC sensor, analyze the thermal conductivity of the gas). For this purpose, the microcontroller can use calibration data and / or characteristic curves stored in the memory and / or perform digital post-processing on the measurement values. Collecting a large number of measurement values at different sensor voltages V S can also compensate for the cross-sensitivity of other physical parameters (such as humidity), which affect the output voltage V OUT .

[0039] In the shown embodiment, the control circuit 40 is a microcontroller with at least one processor. It is designed to execute software instructions stored in the memory to perform the functions described here, such as controlling the measurement time interval (measurement period) by outputting a signal V IO at the digital output and controlling the operation of the analog-to-digital converter (see Figure 4 ). Multiple microcontrollers integrate one or more analog-to-digital converters. However, a separate analog-to-digital converter can also be used. In Figure 8 and Figure 9In the example, a multiplexer and a single analog-to-digital converter can also be used instead of two analog-to-digital converters, where two analog measurement values are successively digitized by means of the multiplexer together with the analog-to-digital converter. However, the control circuit 40 does not necessarily include a processor for executing software instructions, but can also include one-time programmable (OTP) or hard-wired digital circuits that provide substantially the same functions.

[0040] The functions of the above embodiments implement a method for operating a sensor circuit having at least one resistive sensor element and a first circuit node and a second circuit node for applying a sensor voltage. According to the examples described herein, the method includes charging a capacitor (see, for example Figure 4 or Figure 6 , capacitor C 1 ) by coupling it to a voltage source that provides a supply voltage between a first power supply connection and a second power supply connection (as Figure 4 shown, power supply connections SUP and GND), where the first circuit node of the sensor circuit is connected to the first power supply connection. The method further includes coupling the charged capacitor to the second circuit node of the sensor circuit during a measurement time interval such that the sensor voltage obtained between the first circuit node and the second circuit node of the sensor circuit is greater than the supply voltage (see Figure 5 , V S is greater than V SUPPLY , because V N3 becomes negative).

[0041] According to one embodiment, the output voltage of the sensor circuit can be measured during the measurement time interval (e.g., by means of an analog-to-digital converter, see, for example Figure 4 and Figures 7 - 9 ). The measurement time interval can be indicated by a logic signal, which is generated, for example, by a control circuit (such as a microcontroller). According to the embodiment shown herein, at least one resistive sensor element can be part of a Wheatstone bridge. However, the concepts described herein do not depend on a resistive bridge and can also be applied to other resistive sensors. In some embodiments, the sensor voltage can also be measured during the measurement time interval, where the capacitor discharges during the measurement time interval and the sensor voltage thus decreases.

[0042] By digitizing (sampling and quantifying) the output voltage of the sensor circuit and the sensor voltage supplied to the sensor circuit during the measurement time interval, a large number of measurement values can be obtained for different sensor voltages. Especially for TC sensors, this can perform digital post-processing on the measurement values to compensate for cross-sensitivity, such as the cross-sensitivity of the sensor element to humidity.

Claims

1. A circuit device, comprising: The first power supply connector and the second power supply connector (GND), the power supply voltage (V SUPPLY ) is attached between the first power supply connection and the second power supply connection during operation; Having at least one resistive sensor element (R S1 , R S2 ) of a sensor circuit (30), wherein the sensor circuit (30) has a sensor circuit for applying a sensor voltage (V S ), wherein the first circuit node (N1) is connected to the first power supply connector; and A sensor power supply circuit (50) is designed to electrically couple the charged capacitor (C1) to the second circuit node (N2) during a measurement time interval so that the sensor voltage (V S ) is greater than the supply voltage (V SUPPLY ).

2. The circuit arrangement according to claim 1, in, During the measuring time interval, the charged capacitor (C1) is connected between the second supply connection (GND) and the second circuit node (N2) of the sensor circuit (30), so that the sensor voltage (V S ) corresponds essentially to the supply voltage (V SUPPLY ) and the capacitor voltage (V C ) and.

3. The circuit arrangement according to claim 1 or 2, in, The sensor power supply circuit (50) has an electronic switch (T1) which is designed to be switched based on a logic signal (V IO ) connects the charged capacitor (C1) to the second circuit node (N2).

4. The circuit arrangement according to claim 3, The sensor supply circuit (50) has a further electronic switch (D1, T1) which is designed to disconnect the charged capacitor (C1) from the second supply connection (GND) during the measuring time interval.

5. The circuit arrangement according to claim 1 , wherein the at least one resistive sensor element (R S1 , R S2 ) is part of a Wheatstone bridge which is supplied with the sensor voltage (V S ).

6. The circuit arrangement according to claim 1, wherein the at least one resistive sensor element (R S1 , R S2 ) is a micro-electromechanical system MEMS integrated in a chip, the resistance of which depends on the thermal conductivity of the analysis gas surrounding the MEMS.

7. The circuit device according to any one of claims 1 to 6, further comprising: A control circuit (40) comprises at least one analog-to-digital converter, the at least one analog-to-digital converter being designed to digitize the output voltage of the sensor circuit (30) during the measurement time interval.

8. The circuit arrangement according to claim 7, The control circuit (40) is further designed to digitize the output voltage of the sensor circuit (30) during the measurement time interval into a voltage corresponding to the sensor voltage (V S ) is proportional to the voltage (V S / 2).

9. The circuit arrangement according to any one of claims 3 and 4 to 6 and dependent on claim 3, further comprising: The control circuit (40) is designed to generate a logic signal (V IO ), where the logic signal (V IO ) indicates the measurement time interval.

10. The circuit arrangement according to claim 8 or 9, The control circuit is supplied with the supply voltage (V SUPPLY ).

11. A method for operating a device having at least one resistive sensor element (R S1 , R S2 ), wherein the sensor circuit (30) has a sensor circuit for applying a sensor voltage (V S ) a first circuit node (N1) and a second circuit node (N2); the method comprising: The capacitor (C1) is charged by coupling the capacitor (C1) to a voltage source, which provides a supply voltage (V SUPPLY ), wherein the first circuit node (N1) of the sensor circuit (30) is connected to the first power supply connector; as well as The charged capacitor (C1) is coupled to the second circuit node (N2) of the sensor circuit (30) during a measurement time interval, so that the sensor voltage (V S ) is greater than the supply voltage (V SUPPLY ).

12. The method according to claim 11, further comprising: The output voltage (V OUT ).

13. The method according to claim 12, further comprising: Generates a logic signal (V IO ).

14. The method according to any one of claims 11 to 13, in, The at least one resistive sensor element (R S1 , R S2 ) is part of a Wheatstone bridge.

15. The method according to any one of claims 11 to 14, further comprising: The sensor voltage (V S ), wherein the capacitor (C1) is discharged during the measurement time interval so that the sensor voltage (V S )reduce.

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