SU1003333A1 - Voltage-to-frequency converter - Google Patents

Description

The invention relates to a measurement technique and can be used in control systems and automation systems as a measuring voltage generator to frequency. A voltage to frequency converter containing a passive integrating RC circuit, a comparator on an operational amplifier and a diode bit tl3 is known. The disadvantage of this converter is low accuracy in a wide frequency range due to the low accuracy of the passive RC integrator and fixed time of capacitor discharge integrator. A voltage to frequency converter is known, which contains a key device, the input of which is connected to the input bus, and the output is connected to the integrator input, and a comparator whose output is connected to the control input of the key device t 2 3 Its disadvantage is low accuracy in a wide range frequency caused by the non-linear dependence of the frequency of the output signal from the input voltage at high frequency. This non-linearity is due to finite time delays of the comparator and the key device. The purpose of the invention is to improve the accuracy of a voltage to frequency converter in a wide frequency range. The goal is achieved by introducing a controlled voltage divider into a known voltage-to-frequency converter containing a key device whose input is connected to the input bus and output to the integrator's input, and a comparator whose output is connected to the control input of the key device. , the comparison unit and the peak detector, the input of which is connected to the output of the integrator and the input of the controllable voltage divider, the output to the input of the comparison unit, the output of which is connected to the control input of the controllable divider p voltage, the output of the controllable voltage divider is connected to the input of the comparator. The drawing shows the functional electrical circuit of the converter. The converter contains serially connected input bus 1,

key device 2, integrator 3, controlled voltage divider 4, comparator 5, the output of which is connected to the control input of the key device 2, and the output of the integrator 3 through the series connected peak detector b and comparison unit 7 is connected to the second input of the controlled divider 4 voltage,

The Converter operates as follows.

Convertible voltage from bus 1 through key device 2 goes to integrator 3. Linearly changing voltage from integrator 3 output through controlled divider 4 goes to comparator 5. As soon as the level of linearly varying voltage at the input of comparator 5 reaches the setting of comparator 5, the latter is triggered and switching the key device 2 changes the direction of integration. The times at which the sign of the rise rate of the output voltage of the integrator 3 changes are determined by the setting of comparator 5 and the transfer ratio of the controlled divider 4. The transfer ratio of the controlled divider 4 is specified by the comparison unit 7 depending on the imbalance between the rate of the comparison unit 7 and the value triangular voltage, direct peak detector b. .

in the low frequency range, when the delay time of the comparator 5 and the key of the chevy device 2 is negligible compared to the period of the output frequency of the converter, on the other hand, at the output of the integrator 3, rectified by the peak detector b, it is equal to the setting of the block 7 and the error on it the output is absent, and the transfer ratio of the controlled divider 4 is minimal and equal to the nominal one.

In the high frequency range, when the delay time of the comparator 5 and -key device 2 is comparable to the period of the output frequency of the converter, the amplitude of the linearly varying voltage at the output of the integrator 3 tends to increase, since the real change in the sign of the voltage rise rate of the integrator occurs later than expected from - due to the influence of the delays of the comparator 5 and the key device 2. In this case, between the voltage from the peak detector 6 and the setting of the comparison unit 7, there appears a mismatch that changes the transfer coefficient the claimed divider 4 so that the amplitude of the voltage at its output is increased, causing an earlier actuation of the comparator 5. It will extend as long as the voltage at the output of the integrator 3 becomes equal to the setting unit 7.

Thus, voltage stabilization at the output of integrator 3 in the high-frequency region eliminates the influence of finite time delays of the comparator 5 and the key device 2. This in turn expands the frequency range of the device and eliminates the non-linearity of its characteristics, which leads to increased accuracy devices.

Consequently, the use of a peak detector, a rectifier and a controlled divider in the voltage converter into the frequency converter favorably distinguishes the proposed converter from the known one, since it allows to increase

voltage converter accuracy: to frequency over a wide frequency range.

Claims (2)

Invention Formula A voltage to frequency converter containing a key device whose input is connected to the input bus and an output to an integrator input, and a comparator whose output is connected to the control input of a key device, characterized in that, in order to increase the accuracy of the converter in a wide range frequencies, a controlled voltage divider, a comparison unit and a peak detector are inputted into it, the input of which is connected to the output of the integrator and the input of the controlled voltage divider, the output is connected to the input of the comparison unit whose output It is connected to the control input of a controllable voltage divider, wherein the controllable voltage divider is connected to the input of the comparator. Sources of information taken into account in the examination of 1- Gutnikov B.C. The use of operational amplifiers in measurement technology. L., Energie, 1975, p. 105, fig. 48a. 2. Instruments and experimental techniques, 1979, 1, p. 143-145 (prototype).