Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Patent
1997-01-06
1998-11-03
Gaffin, Jeffrey A.
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
341128, 341120, 341172, H03M 134
Patent
active
058315683
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention refers to a process for the analog/digital conversion of an electric signal and a device for implementing the process. From the technical manual by U. Tietze and Ch. Schenk, edition 1971, pp 536-537, a process and a device for the analog/digital conversion of an electric signal are known, which are based on a double integrating precess. An integrator is set to the initial value zero in a first integrating step. In a second integrating step, the input voltage to be converted is integrated upward by the integrator to a predetermined time. Following completion of this predetermined time, a known reference voltage is fed to the integrator in a third process step in place of the voltage to be converted, which then integrates downward until the integrator once more reaches the initial value of zero. The time needed to integrate down is evaluated as a measure for the voltage to be converted. The elements required for the known double integrating process, for example an integrator, a comparator, a clock generator, a control logic as well as a counter are nowadays all components of integrated circuits.
SUMMARY OF THE INVENTION
It is the object of the invention to describe a process for the analog/digital conversion of an electric signal as well as a device for implementing this process, which can be realized simply, especially in connection with a microprocessor.
The solution to this problem is achieved by a process which includes the steps of connecting a capacitor with a first port to a fixed potential (GND), charging the capacitor up to a voltage to be converted by transmitting the converted voltage to a second port of the capacitor, comparing the voltage at the capacitor to a reference voltage and determining a recharging direction by selecting an operating voltage from a variable voltage source, recharging the capacitor by connecting the second port via a current-limiting element to the selected operating voltage which is higher or lower than the reference voltage, determining the time for the voltage change at the capacitor to reach the reference voltage and evaluating the determined time as a measure for the voltage to be converted.
The object of the invention is further achieved by a device for the analog/digital conversion of an electric voltage, the device including a capacitor having a first port which is connected to a fixed reference potential (GND) and a second port for receiving the voltage to be converted, a selector switch, an integrating resistor as a current-limiting element where the capacitor is connected to a voltage source via the selector switch and the integrating resistor, a comparator for switching the selector switch to one of a plurality of voltage sources and comparing the voltage at the capacitor with a reference voltage, wherein the direction of recharging the capacitor is determined by the selection of one of the plurality of voltage sources, and a time detector connected to the comparator for receiving the comparator output signal and for determining the time for the voltage change to reach the reference voltage at the capacitor wherein the determined time is evaluated as a measure for the voltage to be converted.
Advantages of the invention
The process according to the invention for the analog/digital conversion of an electric signal has the advantage that a relatively high accuracy can be achieved, which only depends on the tolerance of a resistance capacitor combination (RC component). One essential advantage is the particularly cost-effective realization, which requires few structural components. Particularly suited for the realization of this invention is a microprocessor, which does not have to comprise an analog/digital converter as a result of the process according to the invention.
In a first process step, the capacitor for the RC component is charged up to the voltage to be converted. In a second process step, the capacitor is connected via a current-limiting component to a voltage source, for which the voltage is higher or lo
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patent: 4876544 (1989-10-01), Kuraishi
patent: 5200752 (1993-04-01), Goeke
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patent: 5384570 (1995-01-01), Dedic
U. Tietze et al.: "Halbleiter-Schaltungstechnik". Springer-Verlag, 1971, pp. 536-537.
Gaffin Jeffrey A.
Huynh Kim N.
Robert & Bosch GmbH
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