16-11-2012, 05:17 PM
VOLTAGE TO FREQUENCY CONVERTER: MODELING AND DESIGN
VOLTAGE TO FREQUENCY CONVERTER.pdf (Size: 1.86 MB / Downloads: 425)
Abstract
In this thesis a study on conventional voltage to frequency converter is given. A linear voltage to frequency converter is assumed i.e. the output frequency level changes with the varying input voltage level. Then as per the findings of our study a voltage to frequency converter is designed and a physical model of the designed circuit is prepared. A transformer and full wave rectifier are used to reach the optimal dc voltage level while the regulator is used for controlled power supply. An op-Amp based voltage to frequency converter is designed whose output is obtained through a 555 timer. The main operation of the op-Amp is to serve as a voltage integrator which is necessary for triangular wave generation and also as a comparator for converting the triangular wave into square wave. The timer circuit is operated in monostable mode. A simple and low cost voltage to frequency converter design and its performance analysis is the main objective of this thesis.
Introduction
A voltage-to-frequency converter (VFC) is an oscillator .Its frequency is linearly proportional to the control voltage. The voltage to frequency (VFC)/counter ADC is monotonic and free of missing codes. It integrates noise and can consume very small amount of power. The voltage to frequency converter(VFC) is also very useful for telemetry applications, since the VFC, which is cheap ,small, and low-powered can be mounted on the experimental subject (patient, artillery shell, wild animal, communication etc.) and communicate with the counter by the telemetry link
A Current-Steering VFC:
The current-steering multi vibrator VFC is actually a current-to-frequency converter rather than a VFC, but, as shown in Figure 2, practical circuits invariably contain a voltage-to-current converter at the input side. The principle of operation is that: the current discharges the capacitor until the threshold is reached, and when the c terminals of the capacitor are reversed, the half-cycle is repeats itself again. The waveform across the capacitor is obtained a linear triangular wave, but the waveform on either terminal with respect to ground is the more complex waveform shown.
Voltage to frequency converter
The Voltage to frequency converter is accepting voltage input and converting it into frequency. The voltage to frequency converter works on the principle of current integrator and comparator. The Voltage to frequency converter in the first stage integrate the dc voltage input and that is converted in to a ramp signal that signal is compared with a comparator which provides either +V or –V output and that is again feed back to the integrator so the integrator output is a triangular wave .The slope of the triangular wave or ramp signal is proportional to the input analog voltage. The comparator section compares the integrator output with zero reference and generates the square wave.