Temperature sensing device with a diode and an analog-to-digital converter

Abstract

Temperature sensing device (200) with a diode (20), in particular a semiconductor diode, and an analog-to-digital converter (22), wherein an output voltage signal of the diode (20) can be applied to an input of the analog-to-digital converter (22), characterized in that the temperature sensing device (200) is designed to couple a reference voltage of the analog-to-digital converter (22) and a diode current of the diode (20) in such a way that the effects of fluctuations in the reference voltage or the diode current on a digital output signal (24) of the analog-to-digital converter (22) are partially or completely suppressed.

Description

[0001] The present invention relates to a temperature sensing device with a diode and an analog-to-digital converter, a measuring device comprising the temperature sensing device according to the invention, a method for digitally determining a temperature, and a method for suppressing temperature effects on the determination of a quantity to be measured. State of the art

[0002] Temperature sensing devices are known from the prior art which exploit the fact that the characteristic curve of a diode has a strong temperature dependence.

[0003] It is also known to integrate such temperature sensing devices into measuring devices that include a sensor for detecting a quantity to be measured, where the sensor's output signal depends on the ambient temperature. Examples of such sensors are micromechanical pressure, acceleration, or angular rate sensors. For their use in corresponding applications, it is necessary to calculate a value of the quantity to be measured that is independent of the ambient temperature.

[0004] In many micromechanical sensors, the measured quantity, for example pressure, acceleration or rotation rate, is detected by the change in piezoelectric resistances or capacitances and converted into an electrical voltage.

[0005] The ambient temperature is a disturbance variable that affects the electrical output voltage of the sensor element. To compensate for the influence of the ambient temperature within an integrated circuit, it must also be detected. Resistors or diodes are used to measure the temperature. To generate a temperature-dependent voltage, diodes are typically supplied with a constant current.

[0006] Signal conditioning for temperature compensation, amplification, or linearization is implemented using digital integrated circuits. Analog-to-digital converters are used to convert the analog electrical voltages from the diode and sensor element into a digital numerical value that can be processed by a computing unit.

[0007] To minimize conversion errors due to fluctuations in the supply voltage of the pressure signal, the pressure sensor and analog-to-digital converter are operated with the same supply voltage. This ensures that when the supply voltage decreases, the sensitivity of the pressure sensor decreases, and consequently, the sensitivity of the analog-to-digital converter increases inversely proportionally, thus keeping the digital value at the output of the analog-to-digital converter unchanged (ratiometric measurement).

[0008] The diode is operated with a constant current that is largely independent of the supply voltage, so the diode's output voltage is also largely independent of the supply voltage. If the supply voltage drops, the diode delivers an unchanged output voltage, while the sensitivity of the analog-to-digital converter (ADC) increases, resulting in a higher digital value at the ADC's output. This leads to a misinterpretation of the diode's output voltage and an incorrect measurement after temperature compensation in the signal path. Disclosure of the invention

[0009] According to the invention, a temperature sensing device is provided with a diode, in particular a semiconductor diode, and an analog-to-digital converter. An output voltage signal of the diode can be applied to an input of the analog-to-digital converter. The temperature sensing device is designed to couple a reference voltage of the analog-to-digital converter and a diode current of the diode in such a way that the effects of fluctuations in the reference voltage or the diode current on the digital output signal of the analog-to-digital converter are partially or completely suppressed.

[0010] A reference voltage is any voltage with which the analog-to-digital converter compares the input voltage applied to its input and on the basis of which the analog-to-digital converter generates a digital output signal. In the context of the invention, a reference voltage of the analog-to-digital converter can be a supply voltage of the analog-to-digital converter.

[0011] In a particular embodiment, the temperature sensing device comprises a voltage-controlled current source. This voltage-controlled current source can be driven by the reference voltage of the analog-to-digital converter and regulates the diode current in such a way that the effects of fluctuations in the reference voltage on the digital output signal of the analog-to-digital converter are partially or completely suppressed.

[0012] For example, a change in the supply voltage of the analog-to-digital converter leads to a change in offset and sensitivity. Changes in offset and sensitivity result in a change in the digital numerical value after the analog-to-digital conversion.

[0013] A change in the digital value at the same temperature and diode current would be interpreted as a change in the temperature. However, by regulating the diode current with the voltage-controlled current source, the change in the digital value is either reduced or eliminated, resulting in a temperature reading that is independent of fluctuations in the supply voltage.

[0014] In a further particular embodiment, the temperature sensing device comprises a current-controlled voltage source. The current-controlled voltage source is driven by the diode current and regulates the reference voltage of the analog-to-digital converter in such a way that the effects of fluctuations in the diode current on the digital output signal of the analog-to-digital converter are partially or completely suppressed.

[0015] Fluctuations in the diode current, at a constant temperature, lead to a change in the output voltage across the diode. This change in output voltage would be interpreted as a change in temperature. By regulating the reference voltage using the current-controlled voltage source, the effects of these diode current fluctuations are compensated for.

[0016] Another aspect of the invention relates to a measuring device with a sensor for detecting a physical quantity to be measured, wherein an output signal of the sensor is temperature-dependent. The measuring device includes a temperature detection device according to the invention. To minimize the influence of temperature on the measurement result, the temperature is determined based on a change in the output voltage of a diode included in the temperature detection device and used for compensation. By using the temperature detection device according to the invention, precise compensation of the temperature influence is possible through an accurate determination of the temperature.

[0017] The measuring device may include a processing unit designed to calculate a measured value of the physical quantity that is largely independent of temperature influence, based on the sensor's output signal and the analog-to-digital converter's digital output signal. This can be achieved, for example, by a calculation formula applied to the digital values ​​for the output voltage of the sensor element and the temperature diode determined within the measuring device.

[0018] The sensor can be, for example, a pressure, acceleration, or rotation rate sensor. It can be designed to detect changes in piezoelectric resistance or capacitance.

[0019] Another aspect of the invention relates to a method for digitally determining a temperature. An output voltage signal of a diode, in particular a semiconductor diode, is applied to an input of an analog-to-digital converter. A digital output signal of the analog-to-digital converter corresponds to a temperature value. A reference voltage of the analog-to-digital converter and a diode current of the diode are coupled in such a way that the effects of fluctuations in the reference voltage or the diode current on the digital output signal of the analog-to-digital converter are partially or completely suppressed.

[0020] In a particular embodiment of the method according to the invention, a voltage-controlled current source is controlled by the reference voltage of the analog-to-digital converter and regulates the diode current in such a way that the effects of fluctuations in the reference voltage on the digital output signal of the analog-to-digital converter are partially or completely suppressed. By using a voltage-controlled current source for the diode current, the output voltage of the diode is compensated so that, for example, a change in the supply voltage of the analog-to-digital converter does not lead to any change in the digital numerical value at the output of the analog-to-digital converter.

[0021] In a further particular embodiment of the method according to the invention, a current-controlled voltage source is controlled by the diode current and regulates the reference voltage of the analog-to-digital converter in such a way that the effects of fluctuations in the diode current on the digital output signal of the analog-to-digital converter are partially or completely suppressed. For example, by using a current-controlled voltage source for the analog-to-digital converter, the supply voltage of the analog-to-digital converter is regulated in a manner dependent on the diode current so that current-induced changes in the diode output voltage do not lead to any changes in the digital numerical value at the output of the analog-to-digital converter.

[0022] Another aspect of the invention relates to a method for suppressing temperature effects on the determination of a quantity to be measured, in particular pressure, acceleration, or rotation rate. Here, a temperature is determined using the inventive method for digital temperature determination. Preferably, a measurement signal of the quantity to be measured is digitized and fed to a processing unit together with the digitally determined temperature. Drawings

[0023] Exemplary embodiments of the invention are explained in more detail with reference to the drawings and the following description. The drawings show:

[0024] Fig. 1 a pressure measuring device according to the state of the art,

[0025] Fig. 2 a pressure measuring device with a temperature sensing device according to a first embodiment of the invention and

[0026] Fig. 3 a pressure measuring device with a temperature sensing device according to a second embodiment of the invention.

[0027] Fig. 1 shows a total with 100 Designated pressure measuring device according to the state of the art with a pressure sensor element 10 , which detects pressure by means of a change in the electrical resistance of a piezoelectric sensor and converts this into an electrical measuring voltage. The measuring voltage is then sent to a first analog-to-digital converter. 12 supplied, which carries a digital signal 14 This generates the signal from the pressure sensor element. 10 ratiometrically converted, that is, pressure sensor element 10 and analog-to-digital converter 12 They are supplied with the same voltage. This minimizes the influence of voltage fluctuations on the pressure sensor element. 10 and the first analog-to-digital converter 12 compensated. The digital signal 14is temperature-dependent and is assigned to a computing unit 30 supplied, which, using one of a total with 200 The temperature measured by the designated temperature detection device is used to calculate a pressure measurement value that is largely independent of the influence of temperature.

[0028] The temperature detection device 200 includes a semiconductor diode 20 , which is supplied by a constant diode current. At the semiconductor diode 20 An output voltage signal is tapped and sent to a second analog-to-digital converter. 22 supplied, which provides a digital temperature value 24 determined and also the computing unit 30 supplies.

[0029] The in Fig. 2 temperature sensing device shown 200 includes a voltage-controlled power source 26 The supply voltage V Bserves as the control voltage for the voltage-controlled current source 26 The output of the voltage-controlled current source 26 supplies the semiconductor diode 20 with a diode current.

[0030] When increasing the supply voltage V B would increase the sensitivity of the second analog-to-digital converter 22 with constant diode current through the semiconductor diode 20 decrease. To compensate for the effect of the lower sensitivity of the second analog-to-digital converter 22 This is compensated for by the voltage-controlled current source. 26 The diode current increases, so the output voltage of the semiconductor diode also increases. The voltage-controlled current source 26 is designed so that the two effects exactly compensate each other and that the digital temperature value 24 from the change in the supply voltage V B is independent.

[0031] Conversely, when the supply voltage V is reduced, B the sensitivity of the second analog-to-digital converter 22 to. The output voltage of the semiconductor diode 20 is reduced by the fact that the voltage-controlled power source 26 the through the semiconductor diode 20 This reduces the flowing diode current. Again, the voltage-controlled current source... 26 designed in such a way that a compensation of the two effects results, so that the digitally determined temperature value 24 remains unchanged.

[0032] The in Fig. The temperature sensing device shown in Figure 3 comprises a current-controlled voltage source. 28 The semiconductor diode 20 The flowing diode current serves as the control current for the current-controlled voltage source. 28 The current-controlled voltage source 28 provides a supply voltage for the second analog-to-digital converter.22 .

[0033] If the diode current decreases, the output voltage of the semiconductor diode also decreases. 20 To reduce the output voltage of the semiconductor diode 20 to compensate and at the output of the second analog-to-digital converter 22 a digital temperature value independent of the diode current 24 To obtain the sensitivity of the second analog-to-digital converter, 22 by lowering the voltage source controlled by the current 28 increased supplied voltage. The current-controlled voltage source 28 is designed so that the digital temperature value 24 remains largely constant when the diode current is varied.

[0034] Conversely, the semiconductor diode 20 The tapped output voltage increases with increasing diode current, so that the current-controlled voltage source 28correspondingly the supply voltage of the second analog-to-digital converter 22 Increased sensitivity of the analog-to-digital converter. 22 is reduced, and the effect of the increase in diode current is exactly balanced.

Claims

[1] Temperature sensing device ( 200 ) with a diode ( 20 ), in particular a semiconductor diode, and an analog-to-digital converter ( 22 ), where an output voltage signal of the diode ( 20 ) at an input of the analog-to-digital converter ( 22 ) can be applied, characterized by , that the temperature detection device ( 200 ) is designed to provide a reference voltage for the analog-to-digital converter ( 22 ) and a diode current of the diode ( 20 ) to couple in such a way that the effects of fluctuations in the reference voltage or diode current on the digital output signal ( 24 ) of the analog-to-digital converter ( 22 ) be partially or completely suppressed. [2] Temperature sensing device ( 200 ) according to claim 1, wherein the temperature sensing device ( 200 ) a voltage-controlled current source ( 26) includes the reference voltage of the analog-to-digital converter ( 22 ) controllable and designed to regulate the diode current in such a way that the effects of fluctuations in the reference voltage on the digital output signal ( 24 ) of the analog-to-digital converter ( 22 ) be partially or completely suppressed. [3] Temperature sensing device ( 200 ) according to claim 1 or 2, wherein the temperature sensing device ( 200 ) a current-controlled voltage source ( 28 ) includes, which is controllable by the diode current and is designed to provide the reference voltage of the analog-to-digital converter ( 22 ) to regulate in such a way that the effects of fluctuations in the diode current on the digital output signal ( 24 ) of the analog-to-digital converter ( 22 ) be partially or completely suppressed. [4] Measuring device ( 100 ) with a sensor ( 10) for detecting a physical quantity to be measured, wherein an output signal of the sensor has a temperature dependence and wherein the measuring device is a temperature detection device ( 200 ) according to one of the preceding claims. [5] Measuring device ( 100 ) according to claim 4, wherein a computing unit ( 30 ) is provided, which is designed to operate based on the sensor's output signal ( 10 ) and the digital output signal of the analog-to-digital converter ( 22 ) to calculate a measured value of the physical quantity that is largely independent of the influence of temperature. [6] Measuring device ( 100 ) according to claim 4 or 5, wherein the sensor ( 10 ) is a pressure, acceleration, or rotation rate sensor. [7] Method for digitally determining a temperature, wherein an output voltage signal of a diode ( 20), in particular a semiconductor diode, at an input of an analog-to-digital converter ( 22 ) is applied and a digital output signal from the analog-to-digital converter ( 22 ) corresponds to a temperature value, characterized in that a reference voltage of the analog-to-digital converter ( 22 ) and a diode current of the diode ( 20 ) are coupled in such a way that the effects of fluctuations in the reference voltage or diode current on the digital output signal ( 24 ) of the analog-to-digital converter ( 22 ) be partially or completely suppressed. [8] Method according to claim 7, wherein a voltage-controlled current source ( 26 ) from the reference voltage of the analog-to-digital converter ( 22 ) is controlled and regulates the diode current in such a way that the effects of fluctuations in the reference voltage on the digital output signal ( 24 ) of the analog-to-digital converter ( 22) be partially or completely suppressed. [9] Method according to claim 7 or 8, wherein a current-controlled voltage source ( 28 ) is controlled by the diode current and the reference voltage of the analog-to-digital converter ( 22 ) regulated in such a way that the effects of fluctuations in the diode current on the digital output signal ( 24 ) of the analog-to-digital converter ( 22 ) be partially or completely suppressed. [10] Method for suppressing temperature effects on the determination of a quantity to be measured, in particular a pressure, an acceleration or a rotation rate, wherein a temperature is determined digitally by using a method according to one of claims 7 to 9. [11] Method according to claim 10, wherein a measurement signal of the quantity to be measured is digitized and combined with the digitally determined temperature of a computing unit ( 30 ) is supplied.

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