SU645262A1 - Voltage-to-frequency converter - Google Patents

Description

trichesky scheme of the proposed device; in fig. 3 - the same, another option; in fig. 4 shows the current-voltage characteristic of the rollover process in the circuit shown in FIG. 3

The device contains a converter /, the input of which is connected in parallel to the reactive element 2, which through the switch 5 is connected to the voltage source 4, the output of the converter / connected to the input signal bus and to the input of the comparator 5, the output of which is connected to the control input of the switch 3.

FIG. Figure 2 shows one of the variants of the circuit diagram of the device proposed, consisting of a functional converter made in the form of a transistor 6 connected according to a common emitter circuit, a capacitor 7, a switch 8, a voltage source (in Fig. 2 - bus 9, comparator 10 , adjusting resistor 11, resistor

12, with the base of transistor 6 connected to one output of resistor 11, the other output of which is connected via a capacitor 7 to a common bus and via a switch 5 to an output of a voltage source 9, which through a resistor 12 is also connected to a collector of transistor 6, an input signal and one the input of the comparator 10, the other input of which is connected to the common bus, and the output of which is connected to the control input of the key 5.

FIG. 3 shows another variant of the circuit diagram of a device for converting voltage into a frequency, which contains a transistor 13, a capacitor 14, a diode 15, a tunnel diode 16, resistors 17 and 18, a capacitor 19, and the capacitor 14 is connected in parallel with the emitter-transistor base

13, the diode 15 is connected in parallel with the base - collector of the transistor 13, the anode of the tunnel diode 16 is connected to the emitter of the transistor 13 and the input signal bus, and the cathode of the diode 16 is connected to the collector of the transistor 13 and through series-connected resistors U7 and 18 with an input signal moreover, parallel to the resistor 17 is on the capacitor 19.

The proposed device operates as follows.

The reactive element 2 is charged from the voltage source 4 for a very short time and when the voltage source 4 is disconnected using a switch 3 is discharged through the nonlinear input resistance of the converter 1 formed by the resistor 11 and the base-emitter junction of the transistor 6 (Fig. 2 ).

The output signal Si of the converter 1 created at the same time creates a current which will be proportional to the current flowing through the input resistance of the converter /. As a result of the addition of the signal 5i from the output of the converter 1 to the signal 52 produced by the voltage converted to the frequency, a signal 5z arises, which is the input signal of the comparator 5.

If the input signal 5z exceeds the allowable switching-on value of the comparator 5, due to the discharge of the reactive element 2, the reactive element 2 will be charged from the voltage source 4 through the key 3. Thus, the voltage on the capacitor 7 changes and, consequently, the voltage changes the signal Si from the converter output / is also changed and the input signal 5 of the comparator 5.

If the input signal S of the comparator 5 is reduced to the hysteresis caused by the value of the shutdown of the comparator 5, then the fast charge of the reactive element 2

stop and slow discharge through the input impedance of the converter / occurs. In this case, the discharge rate determines the frequency of the voltage or current conversion. If the signal changes

S-2, then due to the process described above, the input characteristic range of the converter I will change, in which the voltage on the reactive element 2 varies.

The analysis shows that with a sufficient signal value of 2 compared with the hysteresis of the comparator 5, a stable voltage conversion into

frequency

Another embodiment of a device for converting voltage to frequency using a tunnel diode is shown in

FIG. 3. In this device, if a certain voltage is exceeded or a certain current is measured, a pulse is emitted through the tunnel diode 16. A common bhema composed of transistor 13,

the diode 15 and the capacitor 14, controls the threshold value of the pulse supplied to form the signal S2. Here, the functions of comparator 5, key 3, are performed mainly by the tunnel diode 16.

In order to explain the principle of the circuit, it is necessary to first consider the process of tipping over the current-voltage characteristic of a tunnel diode (Fig. 4). In case the current passing through the transistor 13 exceeds a certain value, the operating point PZ on the current-voltage characteristic will move to the point Pb Under the action of the increased voltage on the tunnel diode 16, the diode 15 will become electrically conductive and the capacitor 14 will quickly charge. The operating point on the characteristic will move in the direction of the point Pa. If, however, with an increase in the base voltage of transistor 13, the collector current reaches a relatively large value, a jump will occur from point Pr to point Pr. The diode 15 will be closed and the capacitor 14 will begin to slowly discharge through the base-emitter portion of the transistor 13. When the PI point is reached, the process will resume.

The principle used in such a scheme makes it possible to make a further generalization, namely, to replace the coincidence circuit made up of a tunnel diode 16 and resistors 17 and 18 with a comparator 10, i.e., the input or arc characteristics (Fig. 2) at the input. If the collector current of transistor 6 exceeds a certain value, the comparator 10 will turn on and capacitor 7 will charge. This charge will stop when the comparator 10 trips threshold voltage is reached. The next discharge of capacitor 7 will then continue until the threshold threshold is reached comparator voltage 10.

By fixing the current, the limits of variation of the base voltage can be changed (Fig. 2). Obtaining the latching current from the voltage to be converted is not a problem, since the threshold value of the comparator is constant and the current is measured only at the time of coincidence.

In contrast to the known, commonly used circuits, in the proposed solution the clamping current or other value changes only at the moment of coincidence. This means that the conversion of the control voltage to a linear current or some other signal can only be carried out at a certain operating point, which is a great advantage compared to the charge of a direct current capacitor, which requires the stability of the current when the output voltage fluctuates. voltage generator current.

The corresponding change in the discharge resistance made, for example, by means of the mentioned adjusting resistor}, connected in series with

the base-emitter section of the transistor 6 allows for an effective linear conversion of voltage to frequency.

The application of the proposed device allows the creation of measurement sensors with frequency output in conjunction with converters of measured values to voltage, which are of great importance for modern automated technology together with the use of computing devices.

Claims (3)

1. A device for converting voltage into a frequency containing a reactive element connected to the width of a voltage source through a key whose control input is connected to the output of a comparator whose input is connected to a thickness of: An input signal, characterized in that, in order to simplify the device while maintaining high conversion accuracy, a functional converter is inputted into it, the input of which is connected in parallel to the reactive element, and the output is connected to the input of the comparator. 2. The device according to claim 1, characterized in that the functional converter is made in the form of a transistor connected in accordance with a circuit with a common element with an adjusting resistor at the input. 3. The device according to claim 1, characterized in that the comparator is made on a tunnel diode, and the key is made on a diode. Sources of information taken into account in the examination: 1.Smolov V. B. Semiconductor encoding and decoding voltage converters. L., “Energie, 1967, p. 276- 283, fig. 3-3. 2. Makhnanov V.D., Milokhin N.T. Devices of frequency and time-impulse transformation. M., "Energy, 1970, with. 34-37. FIG. 2 Fig4