SU760441A1 - Voltage-to-frequency converter - Google Patents

Description

The invention relates to information-measuring technology and is intended for use in digital measuring devices, automatic control devices, and in systems for collecting information processing.

A device for converting voltage into a frequency is known, which contains an integrator, a level detector and a U feedback feedback loop [ΐ].

A disadvantage of the known device is the relatively low stability of the transfer characteristic, due to the instability of the amplitude and duration of the feedback pulse,

Closest to the proposed voltage-to-frequency converter, 20 that contains an integrator on an operational amplifier, the output of which is connected via a commator to 1) —the input of a clocked P-trigger; common bus, and a clock pulse generator, the output of which is connected to the clocking input of the Rtrigger, and the control outputs

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keys are connected to the direct and inverse outputs of the trigger [2],

The disadvantage of this device lies in the low stability of the transfer characteristic, for example, when the ambient temperature changes.

The purpose of the invention is to increase the stability of the transfer characteristics of the Converter.

The goal is achieved by the fact that in a known voltage-to-frequency converter containing an integrator, the output of which is connected via a comparator to the P input. The trigger is a current generator whose output through the first and second keys is connected to the integrator's input and to the common bus. , and the clock pulse generator / output of which is connected to the clock input of the P flip-flop, and the control inputs of the keys are connected to the direct and inverse outputs

P - trigger, the clock pulse generator is made on the reference frequency generator controlled by the generator and mixer, the outputs of the reference frequency generator and the controlled generator are connected to the mixer inputs, and the auxiliary output r3

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The current generator is connected to the control input of a controlled generator. '

The drawing shows the functional electrical circuit of the voltage-to-frequency converter.

The voltage to frequency converter contains an integrator 1, made on an operational amplifier 2 and an integrating capacitor 3, the output of which through a comparator 4 is connected to T> - TE input — trigger 5, current generator 6, made on 7,8,9 and 10 resistors 11, operational amplifier 12 and transistors 13 and 14, the output of which through the first 15 and second 16 keys is connected to the input of the integrator 1 and to the common bus 17, and the control inputs of the first 15 and second 16 keys are connected to the direct and inverse outputs — trigger 5 ', and 18 tact generator s pulse generator 19 provided at the reference frequency and a controlled oscillator 20, whose outputs are connected to inputs of a mixer .21 '. the output of which is connected to the input of the filter 22, the output of which is connected to the clock input ϊ> - flip-flop 5, and the additional output of the current generator 6 is connected to the control input of the controlled generator 20, the input bus 23 and the bus 24 of the negative power source.

Converter voltage to frequency works as follows.

When a positive signal is applied to the input of the integrator 1, the voltage at the output of the operational amplifier 2 decreases linearly, and when the comparator 4 is released, the input 5E - trigger 5 receives a pulse, which translates T> - trigger 5 into the standby mode. Upon receipt of the next clock pulse from the generator 18 clock pulses 13 — trigger 5 is triggered, and a pulse equal in duration to the reciprocal of the frequency of the clock pulses, acting on the control input of the first key 15, closes it, and the second key 16 opens. current is connected to the input of the integrator 1. The discharge of the integrating capacitor 3 with a direct current begins. The voltage at the output of the op-amp 2 increases, and when the threshold of the comparator 4 13 is reached, the trigger 5 goes into the standby state. When the next clock pulse arrives from the generator 18 clock pulses p-trigger 5 is activated, the first key 15 is opened and the second key 16 is closed, the charging of the integrating condeis «« · torus 3 begins again, and the conversion cycle is repeated.

Due to the fact that the output frequency of the device is directly proportional to the hour * of the clock pulses and inversely proportional to the magnitude of the discharge current, with changes in the current _ a stable conversion characteristic ^{5 is} achieved by implementing a directly proportional relationship between the magnitude of the discharge current and the frequency of the clock pulses by using a generator 18 clock pulses, voltage controlled, and a current generator 6 with an additional output.

If the discharge current is unstable, the input control signal of the clock pulse generator changes relative to the nominal value by a relative value, determined by the instability of the discharge current value, and the dependence character is such that as the discharge current increases, the frequency of the clock pulse generator also increases.

The clock pulse generator, which sets a pulse that is stable in duration for discharging an integrating capacitor, must have a high frequency stability, which is achieved by using quartz resonators. However, these generators have a substantially non-linear conversion characteristic and a narrow range of input control signals, which prevents their use as voltage-to-frequency converters.

A small frequency deviation does not allow to use them as a generator of 18 clock pulses, voltage controlled.

The use of two oscillators with quartz frequency stabilization: a reference frequency generator 19 and a controlled oscillator 20, a mixer 21 and a filter 22, which allocates the difference frequency of oscillators 19 and 20, allows to obtain a highly stable voltage controlled oscillator with the required output frequency deviation.

The stabilization of the conversion characteristic is achieved by the change in the collector current of the matched transistor 14 due to the destabilizing factors of the collector current of transistor 13 (discharge current), and a voltage proportional to this current appears on the resistor 9. The voltage on the resistor 9 is the control for the generator 18 clock pulses, which is proportional to the change in voltage, and. It means that the discharge current changes the frequency of the clock pulses. Therefore, the output frequency of the voltage-to-frequency converter remains constant when exposed to destabilizing factors.

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Thus, in the proposed voltage-to-frequency converter, the stability of the conversion characteristic is increased, approaching the stability of the clock pulse generator, including in the case of an unstable current generator. This preserves the linearity of the conversion characteristic of a known device,

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Claims (1)

Claim A voltage converter to a pulse repetition rate containing an integrator, the output of which, through 15, is connected to the I input of a clocked 15 trigger, a current generator whose output through the first and second keys is connected respectively to the integrator input and to a common bus, 20 and a clock generator , the output of which is connected to the clocking input 3) trigger, and the control inputs of the keys are connected to the forward and inverse outputs 15 of the trigger, characterized by the fact that, in order to increase the stability of the characteristic Formations, the clock pulse generator is made on the reference frequency generator, controlled by the generator and; mixer, and · the outputs of the reference frequency generator and a controlled generator are connected to the mixer's inputs, and the auxiliary output of the current generator is connected to the control input of the controlled generator.