SU1190522A1 - Voltage-to-frequency converter - Google Patents

Abstract

A FREQUENCY VOLTAGE CONVERTER containing an integrator with a reset circuit, the input of which is connected to the input bus of the device, and the output to the first input of the comparator, "Resetting their second input which is connected to the source of the reference voltage, characterized in that trigger, oscillator, frequency divider, switch, reversible counter and coincidence circuit are introduced, the counting trigger input is connected to the comparator output, the forward trigger output is connected to the control input of the reset circuit of the integrator the torus and the inverse output to the control input of the switch, the first input of which is connected to the generator output directly, and the second input through the frequency divider, switching outputs (L tel connected to the summation and subtracting inputs of the reversible counter, the information outputs of which are connected to the circuit match, the output of which is connected to the trigger reset input. L SP 1chE fisd

Description

The invention relates to a converter technique and can be used in various digital measuring apparatus.

The aim of the invention is to improve the accuracy by reducing the nonlinearity error due to the finite discharge time of the integrating capacitor, due to the fact that an integrator discharge time interval is inversely proportional to the input voltage.

The use of only digital elements simplifies the design and microelectronic implementation of the device.

FIG. 1 shows the functional diagram of the proposed converter | in fig. 2 - time diagrams of work.

The voltage-frequency converter contains an integrator 1 with a reset circuit, the output of which is connected to the first input of comparator 2, the second input of which is connected to the reference voltage source Up, and also contains trigger 3, generator 4, frequency divider 5, switch 6, reversible counter 7 and a coincidence circuit 8, the counting input of the trigger 3 is connected to the output of the comparator 2, the forward output of the trigger 3 is connected to the control input of the reset circuit of the integrator 1, and the inverse output to the control input of the switch 6, the first input of which is connected to the output of generator 4 directly, and the second input through frequency divider 5, the outputs of switch 6 are connected to the summing and subtracting inputs of the reversible counter 7, whose information outputs are connected to a matching circuit 8 whose output is connected to the reset input of trigger 3 and is the output of the device .

The Converter operates as follows.

Let from the moment t (the voltage Uy is applied to its input. B time 2 voltage (J at the output of integrator 1 reaches the value of the reference voltage source Cdr, which triggers the comparator 2. Thus the voltage is converted (J x in inversely proportional time interval T, (figure 2) according to the formula

Won ""

t -N)

where t, l ,, - i, / is the integrator time constant.

Simultaneously over time T | the accumulation of the output pulses of the generator 4, passing through the frequency divider 5 and the switch 6 to the summing input of the reversing counter 7 (FIG. 2) c), occurs. The number of pulses N, recorded for the time T, to the reversible counter 7 is determined by output.

N --IL

C2J

S.t.

where C is the frequency divider factor of 5; T - the period following the weekend

pulse generator 4. The signal from the output of the comparator 2 at time ig (Fig.28), which characterizes the end of the conversion and Y in the time interval T (, affects the counting input of the trigger 3 and sets the output (Q) to a low level (Fig.2 ), resetting the integrator 1 to the initial state, and the signal from the output (. () of the trigger 3, a high level (Fig. 2d), acting on the control input of the switch 6, blocks the passage of pulses from the output of the frequency divider 5 to the summing reversing input counter 7 (Fig.2zk) and simultaneously allows proh The driving of the generator 4 pulses to the subtracting input (Fig. 2i). Thus, the counting direction of the reversing counter 7 is reversed. The output pulses of the generator 4 subtract the contents of the counter 7 to zero. The countdown time T is determined by the suppression

(3)

.01

at time t, when zeros are written in the reversible counter, the coincidence circuit 8 is triggered and the full (one) conversion cycle ends, which is repeated many times and the output

Converter (figs) enters the frequency in accordance with the expression

(H)

3 where TX T, Tg. (5) Substitutions in the formula (3) N | by its value from formula (2) and substituting from formula (1) the value of T, we get Substituting in the definition (5) the value of neither T, and Tg we have l / st. C, OOP-SL G,. / t 4 ir lVclu; l -4 clJ. The impairments (A) and (6) imply trSi-U, where 5 is the steepness of the transformation determined by the extrusion

(-F)

5..About

(9)

iUon-H

Thus u; (r / l on-JJ 2 u; lc / i.e., both intervals are inversely proportional to the voltage (Jk, and then the period of the frequency TK is also inversely proportional to x e the output frequency of the converter depends linearly on Uy throughout conversion range. The division factor C and the minimum time interval Tg (corresponding to the maximum output frequency of the converter) are chosen based on the need to fully discharge the integrated capacitor Tr the discharge time of the condensate

Claims (1)

FREQUENCY CHAN TO EXIT CONVERTER VOLTAGE - to the first input of the comparator, the second input of which is connected to a reference voltage source, characterized in that, in order to increase accuracy, a trigger, a generator, a frequency divider, a switch, a reversible counter and a matching circuit are introduced into it, and the counting input of the trigger is connected to the output comparator, the direct output of the trigger is connected to the control input of the integrator reset circuit, and the inverse output is connected to the control input of the switch, the first input of which is connected to the generator output directly, and the second input through rer frequency switch outputs are connected to a summing and subtracting input of down counter, whose data outputs are connected to the coincidence circuit, the output of which is connected to the reset input of the flip-flop. 1 1190522