Switching unit for generating an output voltage as a function of a digital data valve and method for calibrating the switching unit
AssigneeSiemens Aktiengesellschaft
InventorDietmar Schwabe
Life of this patent
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Abstract
With analog output stages of digital systems, the relationship between a digital data value, which is assigned to an analog output stage and to an actually generated output voltage, often does not correspond to a desired characteristic curve. A switching unit is provided to generate an output voltage as a function of a digital data value, the characteristic curve of which is adjusted by a calibration voltage. A method for calibrating a corresponding switching unit is also provided. The switching unit and the method are used in controllers.
Claims18
-9. (canceled)
A switching unit for generating an output voltage as a function of a digital data value, comprising:
- a first digital-to-analog converter providing an analog voltage signal which depends on the digital data value;
- a first controllable voltage source generating a calibration voltage as a function of a control value;
- an amplification unit configured to generate the output voltage, wherein a value of the output voltage depends on the analog voltage signal and the calibration voltage;
- a second controllable voltage source generating a reference voltage as a function of a digital control value, the second controllable voltage source being a second digital-to-analog converter,
- wherein the first digital-to-analog converter scales an amplitude of the analog voltage signal as a function of the reference voltage, and
- wherein the digital control value is determined for the second controllable voltage source such that, with a predefined maximum digital data value, a sum of a difference between an actual value of the output voltage and a target value of the output voltage is smaller than a predetermined value.
A method for calibrating a switching unit generating an output voltage by a digital-to-analog converter and by an amplification unit and as a function of a digital data value, comprising:
- assigning a first data value to the digital-to-analog converter, the first data value representing a minimal numerical value of a predetermined value range;
- detecting the output voltage as an actual value of an offset error;
- assigning a second data value to the digital-to-analog-converter, the second data value representing a maximum numerical value of the predetermined value range;
- detecting the output voltage as an actual value of a full scale value;
- applying a calibration voltage to an input of the amplification unit, the calibration voltage being generated as a function of the actual value of the offset error and the actual value of the full scale;
- and
- applying a reference voltage to an input of the digital-to-analog converter, the reference voltage being generated as a function of the actual value of the offset error and the actual value of the full scale.
A control unit, comprising:
- an analog output stage with a switching unit, the switching unit comprising:
- a first digital-to-analog converter providing an analog voltage signal which depends on the digital data value;
- a first controllable voltage source generating a calibration voltage as a function of a control value;
- an amplification unit configured to generate the output voltage, wherein a value of the output voltage depends on the analog voltage signal and the calibration voltage;
- a second controllable voltage source generating a reference voltage as a function of a digital control value, the second controllable voltage source being a second digital-to-analog converter,
- wherein the first digital-to-analog converter scales an amplitude of the analog voltage signal as a function of the reference voltage, and
- wherein the digital control value is determined for the second controllable voltage source such that, with a predefined maximum digital data value, a sum of a difference between an actual value of the output voltage and a target value of the output voltage is smaller than a predetermined value.
Dependencies are inferred from the claim text.