Sensor circuit having compensation resistor for compensating temperature coefficient of bridge circuit

Abstract

The invention relates to a sensor circuit having a compensation resistor for compensating a temperature coefficient of a bridge circuit, comprising a first interface, a second interface and a bridge circuit connected between the first interface and the second interface, the bridge circuit having a plurality of bridge resistors having respective temperature coefficients. The bridge circuit has a measurement sensitivity having a temperature coefficient of the measurement sensitivity and a bridge offset having a temperature coefficient of the bridge offset. The sensor circuit further comprises at least one compensation resistor connected between the first interface and the second interface, and the temperature coefficient of the compensation resistor is different from that of the bridge resistor.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of German Patent Application No. 102023126597.7 filed on September 29, 2023, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The invention relates to a sensor circuit having at least one compensation resistor for compensating the temperature coefficient of a (measurement) bridge circuit. Background Art

[0004] For example, the physical parameter to be measured can be measured by means of a measuring bridge circuit (sensor bridge). In the measuring bridge circuit, half bridges and full bridges are known. A half bridge includes two (bridge) resistors connected as a voltage divider between a first interface (e.g., a power supply interface) and a second interface (e.g., a ground interface), wherein at least one resistor is related to the physical parameter to be measured (e.g., a magnetic field). When the physical parameter to be measured (measurement parameter) changes, the voltage divider ratio of the (measurement) bridge resistor also changes. A full bridge (e.g., a Wheatstone bridge) includes two half bridges connected in parallel between the power supply interface and the ground interface. Here, a differential output signal between the two half bridges can be output according to the measurement parameter.

[0005] The measuring bridge circuit is supplied with a constant voltage or a constant current as supply signal. In both cases, in a full bridge, the difference of the two half-bridge output voltages can usually be used as the sensor output signal. The (measurement) bridge resistance associated with the measured variable and its measurement sensitivity can vary with temperature according to the corresponding temperature coefficient. In the case of tunnel magnetoresistance (TMR) resistors, the temperature coefficient TC of the bridge resistance R and the temperature coefficient of measurement sensitivity TC SB_TMR has a negative sign. That is, the resistance and measurement sensitivity may decrease with increasing temperature.

[0006] In the case of a magnetic field sensor, the measurement sensitivity of a sensor bridge (e.g., a full bridge) can be defined as the change ΔV in the bridge output voltage for a change ΔB in the applied magnetic field. out :S B_Br :=(ΔV out ) / ΔB

[0007] Instead of the magnetic field, other physical measurement variables can of course also be considered.

[0008] However, the output voltage V out The voltage V across the Wheatstone bridge Br Therefore, the measurement sensitivity S of the sensor bridge B0 With VBr Proportional to:

[0009] S B0 ~V Br

[0010] The temperature coefficient of the bridge resistance measurement sensitivity is negative (TC SB_TMR <0), the temperature coefficient TC of the sensor bridge’s measurement sensitivity SB_Br The temperature coefficient of each bridge resistor is negative (TC R <0), the total resistance of the sensor bridge between the power supply interfaces also has a negative temperature coefficient TC R_Br .

[0011] When the sensor bridge is supplied with a constant current as a power supply signal (as may be required in certain applications), the temperature coefficient TC of the total resistance of the sensor bridge R_Br Will affect the bridge voltage V Br ,because

[0012] V Br =R Br I DD ,

[0013] Among them, I DD is a constant supply current.

[0014] Therefore, the temperature coefficient TC of the measurement sensitivity of the sensor bridge supplied with a constant current is SB_Br for:

[0015] TC SB0_Br =T CSB_TMR +TC R_Br .

[0016] Since both temperature coefficients are usually negative, their effects are additive and the temperature behavior of a current-fed sensor is overall worse than the temperature behavior of a voltage-fed sensor bridge.

[0017] If the sensor's operating B field is not in B = 0 mT (for example, when B OP + / -B Range When B OP ≠0), the output voltage (for example, when B=B OP The shift in the bridge resistance over time (e.g. TC) is related to the measurement sensitivity of the bridge resistance. SB_TMR ) will also directly lead to the temperature coefficient TC of the sensor bridge offset Off .

[0018] Therefore, there is a need for a concept for temperature compensation of measurement sensitivity and offset voltage in a sensor (eg, a magnetic field sensor) having a resistive bridge circuit 130 . Summary of the invention

[0019] The device and method of the independent claims meet this need. Advantageous developments are the subject matter of the dependent claims.

[0020] According to a first aspect of the present disclosure, a sensor circuit is proposed. According to some embodiments, the sensor circuit may be, for example, a magnetic field sensor circuit. The sensor circuit includes a first interface (e.g., a power supply interface), a second interface (e.g., a ground interface), and a (measurement) bridge circuit having a measurement sensitivity (sensitivity) connected between the first and second interfaces. According to some embodiments, the bridge circuit may be a half-bridge having a first and a second resistor, wherein at least one resistor is related to a physical parameter to be measured (e.g., a magnetic field), or the bridge circuit may be a full-bridge having two half-bridges. The bridge circuit has a temperature coefficient of measurement sensitivity (measurement sensitivity temperature coefficient). The sensor circuit also includes at least one compensation resistor connected between the first interface (e.g., a power supply interface) and the second interface (e.g., a ground interface), the compensation resistor being configured to at least partially compensate for the temperature coefficient of measurement sensitivity of the bridge circuit (measurement sensitivity temperature coefficient). Therefore, if the bridge circuit has a negative measurement sensitivity temperature coefficient, the compensation resistor may make the measurement sensitivity temperature coefficient positive (zero in an ideal case). If the bridge circuit has a positive measurement sensitivity temperature coefficient, the compensation resistor may make the measurement sensitivity temperature coefficient negative (zero in an ideal case).

[0021] Another aspect of the present disclosure is a sensor circuit, which includes a first interface (e.g., a power supply interface) and a second interface (e.g., a ground interface). The sensor circuit also includes a bridge circuit connected between the first interface (e.g., the power supply interface) and the second interface (e.g., the ground interface). The bridge circuit has a plurality of bridge resistors with corresponding resistance temperature coefficients. The sensor circuit also includes at least one compensation resistor connected between the first interface (e.g., the power supply interface) and the second interface (e.g., the ground interface), the resistance temperature coefficient of the compensation resistor being different from the resistance temperature coefficient of the bridge resistor. The different temperature coefficients of the compensation resistors can compensate for temperature-related changes in the measurement sensitivity and / or offset of the bridge circuit.

[0022] The compensation resistor may be connected directly or indirectly between the first interface (e.g., power supply interface) and the second interface (e.g., ground interface). "Directly" means that the compensation resistor is directly connected to the first interface (e.g., power supply interface) and the second interface (e.g., ground interface), for example, connected in parallel with the bridge circuit. "Indirectly" means that the compensation resistor may be connected in series with other circuit components between the first interface (e.g., power supply interface) and the second interface (e.g., ground interface). For example, the compensation resistor may be arranged in series with the bridge circuit, or may be arranged in series with the bridge resistor within the measuring bridge circuit.

[0023] According to some embodiments, the compensation resistor is independent of the measured variable. Therefore, the compensation resistor does not change depending on the measured variable (eg, magnetic field).

[0024] According to some embodiments, the compensation resistor has a different temperature coefficient (of resistance) than one or more bridge resistors of the bridge circuit. At least partial compensation can be achieved by different temperature coefficients (of resistance).

[0025] According to some exemplary embodiments, a compensating resistor is connected in parallel with the bridge circuit. This may make sense, for example, in the case of a constant current as supply signal.

[0026] According to some exemplary embodiments, a compensating resistor or a further compensating resistor is connected in series with the first and second resistors within the bridge circuit. This may also be useful, for example, in the case of a constant current as supply signal or in order to compensate for the temperature dependency of an offset voltage.

[0027] According to some embodiments, the compensation resistor or another compensation resistor is connected between the output signal interface of the bridge circuit and the second interface (e.g., the ground interface). In other embodiments, the compensation resistor or another compensation resistor may also be connected between the output signal interface of the bridge circuit and the first interface (e.g., the power supply interface).

[0028] According to some embodiments, the temperature coefficient of the measurement sensitivity (sensitivity) of the bridge circuit is negative (TC SB0_TMR <0), the temperature coefficient of the bridge resistance is negative (TC R <0), and the temperature coefficient of the compensation resistor is positive (TC R,comp >0).

[0029] According to some embodiments, the temperature coefficient of the measurement sensitivity of the bridge circuit is positive (TC SB0_TMR >0), the temperature coefficient of the bridge resistance is negative (TC R <0), and the temperature coefficient of the compensation resistor is smaller than that of the bridge resistor (TC R,comp <TC R ).

[0030] According to some embodiments, the temperature coefficient of the measurement sensitivity of the bridge circuit is negative (TC SB0_TMR <0), the temperature coefficient of the bridge resistance is positive (TC R >0), and the temperature coefficient of the compensation resistor is larger than that of the bridge resistor (TC R,comp >TC R ).

[0031] According to some embodiments, the temperature coefficient of the measurement sensitivity of the bridge circuit is positive (TC SB0 TMR >0), the temperature coefficient of the bridge resistance is positive (TC R >0), and the temperature coefficient of the compensation resistor is negative (TC R,comp <0).

[0032] According to some embodiments, the compensation resistor is connected between the first interface (e.g., the power supply interface) and the bridge circuit. According to other embodiments, the compensation resistor is connected between the second interface (e.g., the ground interface) and the bridge circuit. This may make sense, for example, in a constant voltage as the power supply signal.

[0033] According to some embodiments, the temperature coefficient of the measurement sensitivity of the bridge circuit is negative (TC SB0_TMR The compensation resistor is independent of the measured variable and has a smaller temperature coefficient (TC R,comp <TC R ).

[0034] According to some embodiments, the temperature coefficient of the measurement sensitivity of the bridge circuit is positive (TC SB0_TMR The compensation resistor is independent of the measured variable and has a larger temperature coefficient (TC R,comp >TC R ).

[0035] According to some embodiments, the resistance of the bridge circuit is configured as a magnetoresistance resistor. Magnetoresistance is a physical phenomenon in which the resistance of a material is affected by an external magnetic field. There are multiple types of magnetoresistance that may occur in different materials and applications. In anisotropic magnetoresistance (AMR), the resistance of a material varies depending on the direction of an external magnetic field. This phenomenon occurs in some materials with magnetic anisotropy, which means that these materials are preferably magnetized in a specific direction. Giant magnetoresistance (GMR) occurs in thin layer structures consisting of alternating ferromagnetic layers and non-magnetic layers. The resistance of these structures varies with the orientation of the magnetic regions in the layers. GMR is used in magnetoresistance sensor technology (MR sensors) and has important applications in hard disks, magnetic field sensors, and data transmission technology. Colossal magnetoresistance (CMR) is a phenomenon that occurs in specific types of compounds, such as manganese oxides (manganates). At very low temperatures and in the presence of an external magnetic field, the resistance of these materials may drop dramatically. This phenomenon is studied in material research and may be studied in the development of new electronic components. Tunnel magnetoresistance (TMR) occurs in a thin insulator layer between two ferromagnetic electrodes. When the orientation of the magnetic moments in the electrodes changes, the resistance changes greatly. This technology is used in the development of magnetic field sensors and non-volatile magnetic field memories. Extraordinary magnetoresistance (EMR) is a very rare and special phenomenon observed in certain exotic materials. Here, extraordinary magnetoresistance is a very large magnetoresistance effect observed in some high-energy materials. Extraordinary magnetoresistance has potential applications in the development of spintronics and ultrafast electronic components. Different magnetoresistances can be summarized under the term "xMR".

[0036] According to some embodiments, the resistors of the bridge circuit are configured as TMR resistors.

[0037] According to another aspect of the present disclosure, a sensor circuit is proposed. The sensor circuit includes a constant current source, a ground interface, and a bridge circuit connected between the constant current source and the ground interface, the bridge circuit having a negative temperature coefficient of measurement sensitivity (measurement sensitivity temperature coefficient). The bridge circuit includes at least one half-bridge, the half-bridge having a first and a second xMR resistor, the first and second xMR resistors having a negative temperature coefficient (resistance temperature coefficient) respectively. The sensor circuit also includes at least one compensation resistor connected between the constant current source and the ground interface, the compensation resistor substantially not showing magnetic field sensitivity (i.e., non-magnetic resistance) and having a positive temperature coefficient of resistance (resistance temperature coefficient).

[0038] According to some embodiments, the compensation resistor is connected in parallel between the constant current source and the ground interface and is connected in parallel with the bridge circuit.

[0039] According to some embodiments, a compensation resistor or an additional compensation resistor is connected in series with the first and second xMR resistors in the half-bridge.

[0040] According to another aspect of the present disclosure, a sensor circuit is proposed. The sensor circuit includes a constant voltage source, a ground interface, and a bridge circuit having a negative temperature coefficient of measurement sensitivity (measurement sensitivity temperature coefficient). The bridge circuit includes at least one half-bridge having a first and a second xMR resistor, and the first and the second xMR resistor respectively have a negative temperature coefficient of resistance (resistance temperature coefficient). The sensor circuit also includes at least one compensation resistor, which substantially does not show magnetic field sensitivity (i.e., is non-magnetic resistance) and has a negative temperature coefficient of resistance (resistance temperature coefficient). The compensation resistor is connected between the constant voltage source and the bridge circuit, and the bridge circuit is connected between the compensation resistor and the ground interface. Alternatively, the compensation resistor is connected between the bridge circuit and the ground interface, and the bridge circuit is connected between the constant voltage source and the compensation resistor.

[0041] According to some embodiments, a temperature coefficient of resistance of the compensation resistor is smaller than a temperature coefficient of resistance of the first or second xMR resistor.

[0042] According to some embodiments, a further compensation resistor is connected in series with the first and second xMR resistors within the half-bridge, and the sensor circuit has a second parallel half-bridge between the compensation resistor and the ground interface.

[0043] Using the embodiments of the present disclosure, the measurement sensitivity temperature coefficient (TC SB0_Br ) can be reduced in absolute value. For example, in a discrete sensor bridge supplied with a constant current, a parallel resistor with a resistance temperature coefficient of opposite sign compared to the resistance temperature coefficient of the sensor bridge can fine-tune the bridge feed voltage and make the measurement sensitivity more stable over temperature. In a discrete sensor bridge supplied with a constant voltage, a series resistor can have the same effect. In a sensor bridge with a negative measurement sensitivity temperature coefficient (TC SB0 <0), you can choose a resistance with a temperature coefficient of resistance TC RComp <TC R_Br The compensation resistor of the sensor bridge is the positive temperature coefficient of the measuring sensitivity (TC SB0 >0), a resistance temperature coefficient TC RComp >TC R_Br To reduce the temperature dependency of the offset voltage, resistors with defined resistance and temperature coefficients can be placed in the bridge path. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Some examples of the device and / or method are explained in detail below with reference to the accompanying drawings, which are merely exemplary.

[0045] Figure 1A conventional sensor bridge circuit is shown;

[0046] Figure 2 The relationship between the measurement sensitivity temperature coefficient and the offset drift is shown;

[0047] Figure 3 A sensor circuit with a compensation resistor according to a first embodiment is shown;

[0048] Figure 4 The ratio V is shown for different temperature differences ΔT relative to the reference temperature and for different compensation resistors Br (ΔT) / V Br (ΔT=0) and ratio S B0 (ΔT) / S B0 (ΔT=0);

[0049] Figure 5 The ratio V is shown for different temperature differences ΔT relative to the reference temperature and for different compensation resistors Br (ΔT) / V Br (ΔT=0) and ratio S B0 (ΔT) / S B0 (ΔT=0);

[0050] Figure 6 shows a sensor circuit with a compensation diode according to a further embodiment;

[0051] Figure 7 The ratio of the temperature coefficient of the Zener voltage for different temperature differences (% / °C) and (mV / °C) is shown;

[0052] Figure 8 A sensor circuit with a compensation resistor according to a further embodiment is shown;

[0053] Fig. 9 The ratio V is shown for different temperature differences ΔT relative to the reference temperature and for different compensation resistors Br (ΔT) / V Br (ΔT=0) and ratio S B0 (ΔT) / S B0 (ΔT=0);

[0054] Fig.10 shows a sensor circuit with a compensation diode according to a further embodiment;

[0055] Fig.11 A sensor circuit with a compensation resistor according to a further embodiment is shown;

[0056] Fig.12 Shown according to Fig.11The influence of compensation resistance on output voltage offset;

[0057] Fig.13 shows a sensor circuit according to a further embodiment; and

[0058] Fig.14 A further sensor circuit according to an embodiment is shown. DETAILED DESCRIPTION

[0059] Some examples are now described in detail with reference to the accompanying drawings. However, other possible examples are not limited to the features of the embodiments described in detail. They may have modifications of these features and equivalents and alternatives of these features. In addition, the terms used to describe specific examples herein should not limit other possible examples.

[0060] Throughout the description of the drawings, the same or similar reference numerals refer to the same or similar elements or features, which can be implemented in the same or modified form, respectively, while providing the same or similar functions. In addition, in the drawings, the thickness of lines, layers and / or regions may be exaggerated for illustration.

[0061] When two elements A and B are combined using "or", it is understood that all possible combinations, i.e. only A, only B, and A and B, are disclosed, unless otherwise explicitly defined in individual cases. As an alternative expression of the same combination, "at least one of A and B" or "A and / or B" can be used, which corresponds to a combination of more than two elements.

[0062] When singular forms such as "a" and "the" are used and when the use of only one element is neither explicitly nor implicitly defined as binding, additional examples may also use multiple elements to achieve the same function. When the function is subsequently described as being achieved using multiple elements, additional examples may achieve the same function using a single element or a single processing entity. It is further understood that the terms "comprising" and / or "having" when used describe the presence of the features, integers, steps, operations, processes, elements, parts and / or components thereof that are described, but do not exclude the presence or addition of one or more other features, integers, steps, operations, processes, elements, parts and / or components thereof.

[0063] Figure 1 An example of a sensor circuit 100 is shown. A physical variable may be measured using the sensor circuit 100. For example, the sensor circuit 100 may be a magnetic field sensor circuit for measuring an external magnetic field.

[0064] The sensor circuit 100 comprises a power supply interface 110, a ground interface 120 and a measuring bridge circuit 130 connected between the power supply interface 110 and the ground interface 130. The measuring bridge circuit 130 comprises a first half bridge connected between the power supply interface 110 and the ground interface 120 (which has a series circuit consisting of resistors R1 and R2 that are dependent on the measurement variable) and, in parallel with the first half bridge, comprises a second half bridge connected between the power supply interface 110 and the ground interface 120 (which has a series circuit consisting of resistors R3 and R4 that are dependent on the measurement variable). In the illustrated embodiment, the resistors R1 to R4 are magnetoresistive resistors, in particular Figure 1 The two half-bridges shown have TMR resistors with different reference magnetizations.

[0065] There is a first output signal interface V between the resistors R1 and R2 of the first half bridge. out1 There is a second output signal interface V between the resistors R3 and R4 of the second half bridge. out2 . Two output signal interfaces V out1 With V out2 The differential voltage between represents the bridge output voltage V of the sensor circuit 100 that is related to the measured variable (eg, related to the magnetic field). out .

[0066] The measurement sensitivity S of the measurement bridge circuit 130 B_Br can be defined as the bridge output voltage V out Change ΔV when the applied external magnetic field (measured variable) changes ΔB out :S B_Br :=(ΔVout) / ΔB.

[0067] Bridge output voltage V out The voltage V between the power supply interface 110 and the ground interface 120 on the entire (measurement) bridge circuit 130 Br Therefore, the measurement sensitivity S of the bridge circuit 130 is B_Br With V Br Proportional to:

[0068] S B_Br ~V Br .

[0069] Supplying a constant supply current I DD In this case, the voltage is

[0070] V Br =I DD . R Br , where R Br represents the total resistance of the bridge circuit 130, where

[0071]

[0072] When the bridge circuit 130 is supplied with a constant current I DD When (as may be required in specific applications), the total resistance R Br Temperature coefficient TC R_Br Will affect the bridge voltage V Br The temperature coefficient of total resistance TC R_Br The temperature coefficient TC of the individual bridge resistors R1 to R4 that are dependent on the measured variable R Related.

[0073] The temperature coefficient of the measurement sensitivity of the bridge resistors R1 to R4 is negative (TC SB_TMR <0), the temperature coefficient TC of the measurement sensitivity of the bridge circuit 130 SB_Br The temperature coefficient of each bridge resistor R1 to R4 is negative (TC R <0), the total resistance R of the bridge circuit 130 between the power supply interfaces 110 and 120 Br It also has a negative temperature coefficient TC R_Br <0.

[0074] Therefore, the temperature coefficient TC of the measurement sensitivity of the sensor bridge supplied with a constant current is SB_Br for:

[0075] TC SB_Br =TC SB_TMR +TC R_Br

[0076] Because these two temperature coefficients TC SB_TMR and TC R_Br In a TMR bridge resistance is usually negative, so the effects are additive and the temperature characteristics of a current-fed sensor are overall worse than the temperature characteristics of a voltage-fed sensor bridge.

[0077] In addition, the magnetic field B OP Also due to TC SB_TMR A shift occurs, where the output voltage V of the two half-bridges (with different reference magnetizations) out1 、V out2 are the same, that is, V out1 =V out2 , and therefore the differential bridge output voltage V out = 0. The inherent measurement sensitivity (SB TMR ) changes, V out1 =V out2 Move to B≠B OP In B OPThe bridge output voltage V does not disappear. out ≠0, that is, the offset drifts. Therefore, the temperature coefficient TC of the measurement sensitivity of the bridge circuit 130 is SB_TMR The temperature coefficient TC also directly causes the offset of the bridge circuit 130 Off The relationship is Figure 2 Shown in.

[0078] Embodiments of the present disclosure have the goal of at least partially compensating the temperature coefficient TC of the measurement sensitivity of the sensor bridge circuit 130. SB_TMR And thus a sensor circuit is obtained with an ideally vanishing (at least reduced in absolute value) temperature coefficient of measurement sensitivity. Various exemplary embodiments are described below.

[0079] Figure 3 The sensor circuit 300 shown is connected to the power supply interface 110 by a constant current I DD (constant current source) is fed, and further includes a compensation resistor 140 (R comp ). Compensation resistor R comp The temperature coefficient (measurement sensitivity temperature coefficient) TC configured to at least partially compensate for the measurement sensitivity of the bridge circuit 130 SB_Br To this end, the compensation resistor R comp Ideally, it is independent of the measured variable (for example, independent of the magnetic field), and therefore, in the case of the magnetoresistive bridge resistors R1 to R4, for example, non-magnetoresistive. comp Temperature coefficient TC of the bridge resistors R1 to R4 with compensation resistor R Different temperature coefficients TC Rcomp , namely TC Rcomp ≠TC R . Depending on the application or need, TC Rcomp Can be greater or less than TC R .

[0080] In the example shown, the resistance temperature coefficient TC of the bridge resistors R1 to R4 is R is negative (here: −800 ppm / K). This also results in a total resistance R of the bridge circuit 130 Br Negative temperature coefficient of resistance TC R_Br Furthermore, in the example shown, the measurement sensitivity temperature coefficient TC of the bridge circuit 130 is SB_Br Negative (TC SB_Br <0).

[0081] exist Figure 3 In the sensor circuit 300, the compensation resistor R compThe power supply signal interface 110 is connected in parallel to the ground interface 120 and is connected in parallel to the bridge circuit 130. DD In the case of Br As the temperature increases, it decreases. If you choose a resistor with a positive temperature coefficient of resistance TC Rcomp (TC Rcomp >0) compensation resistor R comp , then the negative TC of the bridge circuit 130 R_Br The compensation resistor R comp The parallel connection of is at least partially or completely compensated. Therefore, the compensation resistor R comp can have a negative TC R_Br The bridge circuit 130 is constructed as a resistor with a positive temperature coefficient (PTC resistor). Therefore, the bridge voltage V Br and output voltage V out can be stabilized over temperature. Then, the stabilized output voltage V out The temperature-stabilized measurement sensitivity S of the bridge circuit 130 results from the following formula: B_Br :TC SB_Br =TC SB_TMR +TC R_Overall ,

[0082] Among them, TC R_Overall The bridge circuit 130 and the compensation resistor R comp The resistance temperature coefficient of the parallel circuit.

[0083] According to some embodiments, the compensation resistor R may be selected according to the order of magnitude of the bridge resistors R1 to R4. comp If the bridge resistors R1 to R4 are 4Ω, for example, each, then for example 1 kΩ <R comp Select the compensation resistor R in the range of <10kΩ comp . Compensation resistor R comp Possible materials are metals, PTC thermistors, PTC cold conductors (hot conductors), polymer PTC resistors or (highly doped) polysilicon.

[0084] Figure 4 (Top) The resulting ratio V is shown for different temperature differences ΔT relative to the reference temperature Br (ΔT) / V Br (ΔT=0). Figure 4 (Below) shows the resulting ratio S for different temperature differences ΔT B0 (ΔT) / S B0 (ΔT=0). Here, it is assumed that R1=R2=R3=R4=4kΩ. comp=2kΩ and TC Rcomp = +800ppm / K, achieving a bridge voltage V in the example shown Br and optimal stabilization of the measuring sensitivity of the sensor bridge. Even for TC Rcomp =0, for R comp =2kΩ and R comp =4kΩ to achieve the same as without compensation resistor R comp Therefore, the following embodiments are also conceivable, in which TC Rcomp <0, but TC Rcomp >TC R , where the resistance temperature coefficient TC of the bridge resistors R1 to R4 is R Negative (TC R <0), the measurement sensitivity temperature coefficient of the bridge circuit 130 is negative (TC SB_Br <0), and the resistance temperature coefficient of the compensation resistor is negative (TC Rcomp <0) but greater than TC R (TC Rcomp >TC R ).

[0085] Figure 5 For R comp =2kΩ or 4kΩ and TC Rcomp =0ppm / K or TC Rcomp = +3000ppm / K shows the Figure 4 Similar curves.

[0086] In the case of having a positive resistance temperature coefficient TC R In the case of bridge resistors R1 to R4 associated with the measured variable, some embodiments of the sensor circuit 300 are also conceivable, in which the resistance temperature coefficient TC of the bridge resistors R1 to R4 is R is positive (TC R >0), the measurement sensitivity temperature coefficient of the bridge circuit 130 is positive (TC SB_Br >0), and the resistance temperature coefficient of the compensation resistor is negative (TC Rcomp <0). In addition, the following embodiments are conceivable, in which the resistance temperature coefficient TC of the bridge resistors R1 to R4 is R is positive (TC R >0), the measurement sensitivity temperature coefficient of the bridge circuit 130 is positive (TC SB_Br >0), and the resistance temperature coefficient of the compensation resistor is positive (TC Rcomp >0) but less than TC R (TC Rcomp <TC R ).

[0087] Furthermore, embodiments of the sensor circuit 300 are also conceivable in which the measurement sensitivity temperature coefficient of the bridge circuit 130 is positive (TC SB_Br >0), the resistance temperature coefficient TC of the bridge resistors R1 to R4 R Negative (TC R <0), and the resistance temperature coefficient of the compensation resistor is smaller than the resistance temperature coefficient of the bridge resistor (TC Rcomp <TC R ). In addition, embodiments are conceivable in which the temperature coefficient of measurement sensitivity of the bridge circuit is negative (TC SB_Br <0), the resistance temperature coefficient of the bridge resistor is positive (TC R >0), and the resistance temperature coefficient of the compensation resistor is greater than the resistance temperature coefficient of the bridge resistor (TC Rcomp >TC R ).

[0088] At a constant current I DD In the case of the sensor bridge circuit 130, the additional resistor R comp Connected in parallel with the sensor bridge circuit 30. Constant supply current I DD The additional compensation resistor R comp is allocated between the sensor bridge circuit 130. If the temperature coefficient TC of the compensation resistor Rcomp Greater than the temperature coefficient TC of the total bridge resistance R_Br , then the temperature coefficient of the total circuit 300 is greater than that without the compensation resistor R comp This results in a more stable bridge voltage V over temperature. out . Using compensation resistor R comp Big and positive TC Rcomp It is also possible to achieve a positive temperature coefficient of the total system resistance, which results in a bridge voltage that rises with temperature. This can be used to compensate for the negative temperature coefficient of the measurement sensitivity that is observed at a constant bridge voltage.

[0089] In some embodiments, the compensation resistor R comp May include a component (or a group of components) that is similar to the above Figures 1 to 5 The resistance variation is provided in a similar manner as described above. In some embodiments, the compensation resistor R comp Non-ohmic components may be included.

[0090] Figure 6 The sensor circuit 600 shown is connected to the power supply interface 110 by a constant current I DD(constant current source) is fed and includes a compensation diode 605 (D comp ). Compensation diode D comp The temperature coefficient (measurement sensitivity temperature coefficient) TC configured to at least partially compensate for the measurement sensitivity of the bridge circuit 130 SB_Br To this end, the compensation diode D comp Ideally, it is independent of the measured variable (for example, independent of the magnetic field), that is, in the case of the magnetoresistive bridge resistors R1 to R4, it is, for example, non-magnetoresistive. comp The bridge resistors R1 to R4 have a temperature coefficient TC R Different compensation diode temperature coefficient TC Dcomp , such as TC Dcomp ≠TC R . Depending on the application or requirement, TC Dcomp Can be greater or less than TC R .

[0091] Figure 7 (Left side) shows the Zener voltage Y for different temperature differences (% / °C) z The ratio of the temperature coefficient produced. Figure 7 (Right side) shows the Zener voltage Y for different temperature differences (mV / °C) z The ratio of the temperature coefficient produced.

[0092] Figure 8 The sensor circuit 800 shown is powered by a constant supply voltage V DD (constant voltage source) is fed and includes a compensation resistor 140 (R comp ). Therefore, the compensation resistor R comp However, the compensation resistor R is connected between the power supply interface 110 and the ground interface 120 as a series resistor instead of a parallel resistor. comp In this case, a temperature coefficient (temperature coefficient of measurement sensitivity) TC is also formed for at least partially compensating the measurement sensitivity of the bridge circuit 130 . SB_Br To this end, the compensation resistor R comp Ideally, it is independent of the measured variable (for example, independent of the magnetic field), and is therefore, for example, non-magnetic. comp With compensation resistor R comp The temperature coefficient TC of the bridge resistors R1 to R4 R Different temperature coefficients TC Rcomp , such as TC Rcomp ≠TC R .

[0093] exist Figure 8 In the example shown, the resistance temperature coefficient TC of the bridge resistors R1 to R4 is R is negative (here: -800 ppm / K). The total resistance R of the bridge circuit 130 Br Negative temperature coefficient of resistance TC R_Br In addition, in the example shown, the measurement sensitivity temperature coefficient TC of the bridge circuit 130 is SB_Br Also negative (TC SB_Br <0).

[0094] exist Figure 8 In the sensor circuit 800, the compensation resistor R comp connected between the power supply signal interface 110 and the bridge circuit 130 and having a resistance temperature coefficient TC of the bridge resistors R1 to R4 R Smaller (more negative) temperature coefficient of resistance TC Rcomp (TC Rcomp <TC R ). Therefore, according to Figure 8 , the measurement sensitivity temperature coefficient TC of the bridge circuit 130 SB_Br The compensation resistor is essentially independent of the measured variable and has a resistance temperature coefficient TC that is smaller than the bridge resistor. R The temperature coefficient of resistance TC Rcomp Therefore, at a constant supply voltage V DD In the compensation resistor R comp The voltage drop caused by the bridge circuit 130 is stronger than the voltage drop caused by the bridge circuit 130. Therefore, in the constant supply voltage VDD, the voltage drop V Br Increases with increasing temperature. Fig. 9 This is shown in (above), which shows the resulting ratio V for different temperature differences ΔT Br (ΔT) / V Br (ΔT=0). Fig. 9 (Below) The resulting measurement sensitivity ratio S is shown for different temperature differences ΔT B0 (ΔT) / S B0 (ΔT=0). Figure 7 The different curves with different R from 0kΩ to 8kΩ comp and TC Rcomp =0ppm / K or TC Rcomp =-1600ppm / K related.

[0095] If you choose a resistor with a temperature coefficient of resistance TC Rcomp <TC R The compensation resistor R comp, the negative TC of the bridge circuit 130 can be at least partially or completely compensated. R_Br Since the bridge voltage V Br As ΔT>0 increases, the output voltage V out Can be stabilized over temperature. The stabilized output voltage V out This results in a temperature-stabilized measurement sensitivity S of the bridge circuit 130. B_Br (See Fig. 9 (below)).

[0096] In the case of a positive temperature coefficient of resistance TC R In the case of the bridge resistors R1 to R4 that are dependent on the measured variable, the following embodiments of the sensor circuit 800 are also conceivable, in which the measurement sensitivity temperature coefficient TC of the bridge circuit 130 is SB_Br is positive (TC SB_Br >0), compensation resistor R comp It is independent of the measured variable and has a resistance temperature coefficient TC greater than the bridge resistance. R Large resistance temperature coefficient TC Rcomp (TC Rcomp >TC R ).

[0097] If the bridge 130 is supplied with a constant supply voltage V DD , you can use a temperature coefficient TC Rcomp The series compensation resistor R comp To fine-tune the bridge voltage V Br . Using resistor R comp and temperature coefficient TC Rcomp The appropriate value of the series resistor can compensate for the temperature coefficient of sensitivity TC SB_TMR .

[0098] exist Fig.10 In the sensor circuit 1000, the compensation diode D which is independent of the measured parameter comp connected between the power supply signal interface 110 and the bridge circuit 130 and having a resistance temperature coefficient TC of the bridge resistors R1 to R4 R Smaller (more negative) temperature coefficient of resistance TC Dcomp (TC Dcomp <TC R ). Therefore, according to Fig.10 , the measurement sensitivity temperature coefficient TC of the bridge circuit 130 SB_Br is negative, the compensation diode D comp It is essentially independent of the measured variable and has a temperature coefficient of resistance TC that is smaller than the bridge resistance. R The temperature coefficient of resistance TCDcomp Therefore, at a constant supply voltage V DD In the compensation diode D comp The voltage drop caused by V is stronger than the voltage drop caused by the bridge circuit 130. Therefore, at a constant supply voltage V DD In the example, the voltage drop V caused by the bridge circuit 130 is Br Increases with increasing temperature.

[0099] Fig.11 The sensor circuit 1100 shown is supplied with a constant supply current I DD is fed and comprises a compensation resistor 140 (R 2,series ). Therefore, the compensation resistor R 2,series The compensation resistor R is connected in series with the first resistor R1 and the second resistor R2 in the bridge circuit 130. 2,series Connect to the first output signal interface V out1 Between the compensation resistor R2 and the bridge resistor R3. Other arrangements of the compensation resistors in the first half bridge are also conceivable. 2,series It can be arranged in the second half-bridge R3, R4.

[0100] Therefore, the compensation resistor R 2,series Here, it is also connected between the supply connection 110 and the ground connection 120. In addition, the compensation resistor R 2,series Here, a temperature coefficient of measurement sensitivity TC is also provided for at least partially compensating the bridge circuit 130 . SB_Br To this end, the compensation resistor R 2,series Ideally, it is independent of the measured variable (for example, independent of the magnetic field), that is, for example, non-magnetic resistance. In addition, the compensation resistor R 2,series The bridge resistors R1 to R4 have a temperature coefficient TC R Different temperature coefficients TC R2_series , such as TC R2_series ≠TC R .

[0101] In some embodiments, the compensation resistor R 2,series A component (or set of components) may be included that provides a resistance change in a manner similar to that described above. In some embodiments, the compensation resistor R 2,series Non-ohmic components may be included.

[0102] Fig.12 shows the compensation resistor R with and without additional 2,series In both cases, the output voltage V of the half-bridge branch related to the B field out1 、V out2At room temperature (thin line), V out1 and V out2 In B = B OP is the same when the bridge offset is zero. 2,series In the case of B = B, the bridge resistor R2 associated with the measured variable must be adapted so that OP The thick curve corresponds to the output voltage V at high temperature (HT). out1 、V out2 . By using the negative temperature coefficient of the bridge resistance, the total bridge resistance decreases, and the bridge voltage also decreases at a constant supply current. Therefore, the output voltage V out1 and V out2 The usually negative temperature coefficient of sensitivity TC SB_TMR Resulting in a flatter V OUT -B characteristic, which results in a shift of the zero offset B field towards higher values. OP The bridge offset in is no longer zero, that is, there is a SB_TMR TC Off The straight thick line represents the case without additional compensation resistor R 2,series In the case of V OUT1 / 2 .

[0103] When the resistance temperature coefficient TC is positive R2,series The additional compensation resistor R 2,series When connected in series to bridge resistor R2, the reduction in the total resistance of bridge 130 is reduced, and therefore at higher temperatures, V out1 / 2 The reduction of also decreases, such as Fig.11 In addition, compared with the V OUT2 (Line 904) compared to the additional compensation resistor R 2,series The resistor of the half bridge has V OUT1 This results in a smaller decrease in V out1 and V out2 The intersecting B field will not be as large as without the additional compensation resistor R 2,series (lines 906, 908). Therefore, the offset shift decreases with temperature and thus TC Off Also decreases. Fig.12 It can be seen that the additional compensation resistor R 2,series (Partial) Compensation TC SB_TMR It is also possible to select an additional compensation resistor R 2,series and its temperature coefficient to perform overcompensation in order to achieve TC Off The sign changes.

[0104] The same effect can be achieved by replacing the additional compensation resistor R 2,series However, the additional compensation resistor R 1,series is connected in series with the bridge resistor R1. Alternatively, an additional compensation resistor R 3,series It can also be connected in series with R3. OUT2 The decrease in t is then increased at higher temperatures, which results in a smaller shift of the offset and thus in a smaller TC Off .

[0105] Generally speaking, the bridge 130 is supplied with a constant supply voltage V DD or TC SB_TMR The proposed principle also applies when . In the latter case, the temperature coefficient of resistance of the realized series resistor must also have the opposite sign.

[0106] In general, there are a number of options for arranging series resistors or parallel resistors in a bridge circuit in order to achieve temperature compensation of sensitivity and offset. Fig.13 Shown with the help of Figure 3 and Fig.11 The combination of the embodiments described, wherein the compensation resistor R connected in parallel comp The series compensation resistor R is denoted by reference numeral 140 and is connected to the half-bridge R1, R2. 2,series This is indicated by reference numeral 140'. Figure 8 and Fig.11 The described embodiments can also be combined with each other to form a sensor circuit having a constant voltage source, a ground interface 120 and a bridge circuit 130, the bridge circuit comprising at least one half-bridge with a first and a second xMR resistor, the first and the second xMR resistor each having a negative temperature coefficient. The combined sensor circuit comprises at least one compensation resistor 140 having a negative temperature coefficient, which is smaller than the temperature coefficient of the first or the second xMR resistor. The compensation resistor 140 is connected between the constant voltage source and the bridge circuit 130, and the bridge circuit 130 is connected between the compensation resistor (140) and the ground interface. Alternatively, the compensation resistor 140 is connected between the bridge circuit 130 and the ground interface (120), and the bridge circuit 130 is connected between the constant voltage source and the compensation resistor 140. The additional compensation resistor R 2,series The first and second xMR resistors R1 , R2 are connected in series within the half-bridge ( R1 , R2 ). The combined sensor circuit also has a second parallel half-bridge ( R3 , R4 ) between the compensation resistor 140 and the ground connection 120 .

[0107] Fig.14Two additional examples are shown. In the circuit on the left, each bridge resistor R 11 To R 22 With respectively assigned series compensation resistors. In the circuit on the right, each bridge resistor R 11 To R 22 With respectively assigned parallel compensation resistors.

[0108] In semiconductor components, resistors with a positive temperature coefficient can be realized using materials such as metals or highly doped (polycrystalline) silicon. For example, resistors with a negative temperature coefficient can be realized using low-doped (polycrystalline) silicon.

[0109] The proposed sensor circuit with compensation resistor can achieve more stable temperature characteristics without the cost and additional space required for active temperature compensation.

[0110] The aspects and features described in conjunction with a specific example of the aforementioned examples may also be combined with one or more other examples in order to replace the same or similar features of the other examples or to additionally introduce the features into the other examples.

[0111] It is further understood that the disclosure of multiple steps, processes, operations or functions disclosed in the specification or claims should not be interpreted as being mandatory in the described order, unless this is explicitly stated in individual cases or is mandatory for technical reasons. Therefore, the execution of multiple steps or functions is not limited to a specific order by the foregoing description. In addition, in other examples, a single step, a single function, a single process or a single operation may include and / or be divided into multiple sub-steps, sub-functions, sub-processes or sub-operations.

[0112] If aspects are described in the preceding paragraphs in conjunction with an apparatus or system, these aspects are also to be understood as a description of the corresponding method. In this context, a block, an apparatus or a functional aspect of an apparatus or system may correspond, for example, to features of the corresponding method, such as method steps. Therefore, aspects described in conjunction with a method are also to be understood as a description of the properties or functional features of the corresponding block, corresponding element, corresponding apparatus or corresponding system.

[0113] The following claims are hereby incorporated into the detailed description, wherein each claim may stand on its own as a separate example. It should also be noted that, although a dependent claim refers to a specific combination with one or more other claims in the claims, other examples may also include a combination of the dependent claim with the subject matter of any other dependent claim or independent claim. Such combinations are hereby explicitly proposed, unless it is stated in individual cases that a specific combination is not intended. Furthermore, features of a claim shall also be included by any other independent claim, even when the claim is not directly defined as dependent on the other independent claim.

Claims

1. A sensor circuit (300; 600; 800), comprising: A first interface (110); A second interface (120); a bridge circuit (130) connected between the first interface (100) and the second interface (120), the bridge circuit having a plurality of bridge resistors with corresponding temperature coefficients, The bridge circuit has a measurement sensitivity and a bridge offset, the measurement sensitivity has a temperature coefficient of the measurement sensitivity, and the bridge offset has a temperature coefficient of the bridge offset; and At least one compensation resistor (140) is connected between the first interface (110) and the second interface (120), the temperature coefficient of the compensation resistor being different from the temperature coefficient of the bridge resistor.

2. The sensor circuit (300; 600; 800) according to claim 1, wherein: The compensating resistor (140) is independent of the measured variable.

3. The sensor circuit (300; 600; 800) according to any one of the preceding claims, wherein: The compensation resistor (140) is connected between the first interface (110) and the second interface (120) and is connected in parallel with the bridge circuit (130).

4. The sensor circuit (300; 600; 800) according to claim 3, wherein: A further compensating resistor (140') is connected in series with the bridge resistor in the bridge circuit (130).

5. The sensor circuit (300; 600; 800) according to any one of the preceding claims, wherein: The temperature coefficient of the measurement sensitivity of the bridge circuit (130) is negative, the temperature coefficient of the bridge resistance is negative, and the temperature coefficient of the compensation resistance (140) is positive.

6. The sensor circuit (300; 600; 800) according to any one of claims 1 to 4, wherein: The temperature coefficient of the measurement sensitivity of the bridge circuit (130) is positive, the temperature coefficient of the bridge resistance is negative, and the temperature coefficient of the compensation resistance (140) is smaller than the temperature coefficient of the bridge resistance.

7. The sensor circuit (300; 600; 800) according to any one of claims 1 to 4, wherein: The temperature coefficient of the measurement sensitivity of the bridge circuit (130) is negative, the temperature coefficient of the bridge resistance is positive, and the temperature coefficient of the compensation resistance (140) is greater than the temperature coefficient of the bridge resistance.

8. The sensor circuit (300; 600; 800) according to any one of claims 1 to 4, wherein: The temperature coefficient of the measurement sensitivity of the bridge circuit (130) is positive, the temperature coefficient of the bridge resistance is positive, and the temperature coefficient of the compensation resistance (140) is negative.

9. The sensor circuit (300; 600; 800) according to claim 1 or 2, wherein: The compensation resistor (140) is connected in series with the bridge resistor in the bridge circuit (130).

10. The sensor circuit (300; 600; 800) according to claim 1 or 2, wherein: The compensation resistor (140) is connected in series with the bridge circuit (130).

11. The sensor circuit (300; 600; 800) according to claim 10, wherein: A further compensating resistor is connected in series with the bridge resistor in the bridge circuit (130).

12. The sensor circuit (300; 600; 800) according to claim 11, wherein: The additional compensation resistor is connected between the output signal interface of the bridge circuit (130) and one of the first interface (110) or the second interface (120).

13. The sensor circuit (300; 600; 800) according to any one of claims 10 to 12, wherein: The temperature coefficient of the measurement sensitivity of the bridge circuit (130) is negative, and the compensation resistor (140) has a temperature coefficient smaller than the temperature coefficient of the bridge resistor.

14. The sensor circuit (300; 600; 800) according to any one of claims 10 to 12, wherein: The temperature coefficient of the measurement sensitivity of the bridge circuit (130) is positive, and the compensation resistor has a temperature coefficient greater than the temperature coefficient of the bridge resistor.

15. The sensor circuit (300; 600; 800) according to any one of the preceding claims, wherein: The bridge circuit (130) has a first half-bridge and a parallel second half-bridge.

16. The sensor circuit (300; 600; 800) according to any one of the preceding claims, wherein: The bridge resistors of the bridge circuit (130) are designed as xMR resistors.

17. The sensor circuit (300; 600; 800) according to claim 16, wherein: The bridge resistors are designed as TMR resistors.

18. A sensor circuit (300), comprising: Constant current source; A grounding interface (120); a bridge circuit (130) connected between the constant current source and the ground interface (120), the bridge circuit comprising at least one half-bridge, the half-bridge having first and second xMR resistors, the first and second xM resistors having negative temperature coefficients respectively; and At least one compensation resistor (140) is connected between the constant current source and the ground interface (120) and connected in parallel with the bridge circuit, and the compensation resistor has a positive temperature coefficient.

19. The sensor circuit (300; 600; 800) according to claim 18, wherein: A further compensating resistor is connected in series with the first and second xMR resistors in the half bridge, wherein the further compensating resistor has a temperature coefficient that is different from a temperature coefficient of the xMR resistors.

20. The sensor circuit according to claim 18 or 19, wherein: The bridge circuit (130) also includes a second half-bridge parallel to the half-bridge.

21. A sensor circuit (600), comprising: Constant pressure source; A grounding interface (120); A bridge circuit (130), the bridge circuit comprising at least one half-bridge, the half-bridge having a first xMR resistor and a second xMR resistor, the first and second xMR resistors respectively having a negative temperature coefficient; and at least one compensation resistor (140), the compensation resistor having a negative temperature coefficient, wherein the temperature coefficient of the compensation resistor (140) is less than the temperature coefficient of the first xMR resistor or the second xMR resistor, wherein the compensation resistor (140) is connected between the constant voltage source and the bridge circuit (130), and the bridge circuit (130) is connected between the compensation resistor (140) and the ground interface, or The compensation resistor (140) is connected between the bridge circuit (130) and the ground interface (120), and the bridge circuit (130) is connected between the constant voltage source and the compensation resistor (140).

22. The sensor circuit (300; 600; 800) according to claim 21, wherein: A further compensating resistor is connected in series with the first xMR resistor and the second xMR resistor in the half bridge, wherein the further compensating resistor has a temperature coefficient that is different from a temperature coefficient of the xMR resistors.

23. The sensor circuit according to claim 21 or 22, wherein: The bridge circuit (130) also includes a second half-bridge parallel to the half-bridge.

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