RU2802872C1 - Integrating analog-to-digital converter - Google Patents

Abstract

FIELD: measuring; computer technology.

SUBSTANCE: used in digital measuring instruments, as well as in systems for digital processing of analog information. For this, an integrating analog-to-digital converter is proposed, which contains the first 1, second 2 and third 3 analog switches, adder 5, first 6 and second 7 integrators, comparator 8, pulse shaper 9, clock pulse generator 10, two-input element AND 11, RS mode trigger 12, binary counter 13, three-input AND element 14, delay element 15, converter input 16, reference voltage input 17, converter start input 18, binary counter 13 has the following inputs: counting 19, reading 20 and zeroing 19, binary counter outputs.

EFFECT: increase in the speed of the converter due to the combination of the operation of integrating the input signal and the compensation integration of a linearly changing exemplary signal of opposite polarity.

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Description

The invention relates to measuring and computing technology and can be used in digital measuring instruments, as well as in systems for digital processing of analog information.

Analog-to-digital converters are well known, which are based on structures with push-pull (compensation) integration (SU 220622 A1, SU 132863 A1, SU1381709 A1, SU1405116 A1).

The encoding process in these converters includes two main stages (cycles). At the first stage, the input signal is integrated over a fixed time interval. On the second stage, the integrator is discharged with a reference voltage having a sign opposite to the input voltage. The time interval of the discharge turns out to be directly proportional to the converted value and its coding leads to obtaining a digital equivalent of the measured value. Due to the suppression of interference received at the input of the device, converters of this type have increased noise immunity and accuracy.

The closest in technical essence to the claimed device is an integrating analog-to-digital converter (SU 1410274 A1), containing an integrator, a clock generator, an R-S mode trigger, a binary counter, a comparator, a pulse shaper, a delay element, three analog switches, and a two-input AND element.

The disadvantage of the converter is the long time spent on obtaining a digital reading.

The purpose of the invention is to increase the speed of the converter by combining the operation of integrating the input signal and compensatory integration of a linearly varying reference signal of the opposite polarity.

This goal is achieved by the fact that in a known integrating analog-to-digital converter containing a first integrator, a clock pulse generator, an R-S mode trigger, a binary counter, a comparator, a pulse shaper, a delay element, three analog switches, a two-input AND element, the input of the first analog switch is connected with the converter input, the second input is with the reference voltage input, the output of the first integrator is connected to the first input of the comparator and, through the third analog switch, to the ground bus of the converter, the second input of the comparator is connected to the ground bus, and the output, through a pulse shaper, is connected to the read input binary counter, the reset input of the R-S mode trigger, to the control input of the third analog switch and through a delay element to the reset input of the binary counter, the output of the clock pulse generator is connected to the first input of the two-input AND element, the second input of which is connected to the start input of the converter, and the output is connected to The S-input of the R-S mode trigger, additionally introduced the second integrator, the fourth analog switch, the adder and the three-input AND element, the control inputs of the first and second analog keys are connected to the output of the R-S mode trigger and with the first input of the three-input AND element, the second input of which is connected to the output of the generator clock pulses, and the first input is with the output of the comparator, the output of the three-input element And is connected to the counting input of the binary counter, the output of the first analog key is connected to the first, and the output of the second analog key through the second integrator is connected to the second input of the adder and the output of the fourth analog key, input which is connected to the ground bus, and the control input is connected to the output of the pulse shaper.

The inventive device is distinguished by the presence of a second integrator, an adder, a fourth analog switch and a three-input element and their connections with other converter blocks.

The analysis shows that the introduction of these blocks allows us to reduce the time spent on coding by at least two times.

In fig. 1 shows a block diagram of an integrating analog-to-digital converter; FIG. 2 is a functional diagram of the converter, and in FIG. 3 - timing diagram explaining the operation of the converter.

The integrating analog-to-digital converter contains the first 1, second 2 and third 3 analog switches, adder 5, first 6 and second 7 integrators, comparator 8, pulse shaper 9, clock pulse generator 10, two-input element AND 11, R-S mode trigger 12, binary counter 13, three-input element AND 14, delay element 15, converter input 16, reference voltage input 17, converter start input 18, binary counter 13 has the following inputs: counting 19, reading 20 and resetting 19, binary counter outputs 22.

The integrating analog-to-digital converter (Fig. 1) operates as follows.

At moment t _0, a pulse from the clock pulse generator (GTI) 10 is released at the output of the two-input element AND 11, which coincides in time with the trigger signal coming from input 18. This pulse turns the RS trigger of mode 12 into a single state. In this case, the first 1 and second 2 analog switches are closed and the three-input element 14 is opened. The reference voltage –E is supplied to the input of the second integrator 7, and at the output the formation of an exemplary linearly varying voltage U ₀ = - K (t – t ₀ ) begins, where K = E/R ₁ C ₁ . This voltage is supplied to the second input of the adder, the first input of which is simultaneously supplied with input voltage U _x through open analog switch 1 from input 16. The voltage from the output of adder 5 is supplied to the input of the first integrator 6:

U _input = U _x - K (t – t ₀ )

In this case, a voltage is formed at its output:

U _out = U _x (t – t ₀ )/RC - K (t – t ₀ ) ² /RC (Fig. 3),

At the same time, through the open three-input element AND 14, the binary counter 13 is filled. The process continues until time t ₁ (Fig. 3), when the voltage at the output of the first integrator 6 becomes equal to zero:

U _out = U _x T _x / RC - K T _x ² / RC = 0, (1)

where Тх = t ₁ – t ₀

At this moment, the comparator 8 goes to the zero state, the shaper 9 generates a pulse, which reads information from the outputs of the counter, resets the R-S mode trigger and, after a time interval determined by the delay element 15, transfers the binary counter 11 to its initial state.

From equation (1) we obtain:

U _x = K Tx /2 (2)

Expressing the time interval T _x through the numerical equivalent N of the code received at time t ₁ in binary counter 13, we can write:

U _x = NКτ/2 + КΔt/2,

where Kτ/2 determines the quantization step of the converter by level, Δt is the quantization error of the Tx time interval, and KΔt/2 is the quantization error of the converted signal by level.

Claims (1)

An integrating analog-to-digital converter containing a first integrator, a clock pulse generator, an R-S mode trigger, a binary counter, a comparator, a pulse shaper, a delay element, three analog switches, a two-input AND element, the input of the first analog key is connected to the input of the converter, the input of the second is connected to reference voltage input, the output of the first integrator is connected to the first input of the comparator and, through the third analog switch, to the ground bus of the converter, the second input of the comparator is connected to the ground bus, and the output, through a pulse shaper, is connected to the read input of the binary counter, the reset input of the R-S mode trigger, to control input of the third analog switch and through a delay element to the binary counter reset input, the output of the clock pulse generator is connected to the first input of the two-input AND element, the second input of which is connected to the start input of the converter, and the output is connected to the S-input of the R-S mode trigger, characterized in that that a second integrator, a fourth analog switch, an adder and a three-input AND element are introduced into it, the control inputs of the first and second analog keys are connected to the output of the R-S mode trigger and to the first input of the three-input AND element, the second input of which is connected to the output of the clock pulse generator, and the first input - with the output of the comparator, the output of the three-input element AND is connected to the counting input of the binary counter, the output of the first analog switch is connected to the first, and the output of the second analog switch through the second integrator - to the second input of the adder and the output of the fourth analog switch, the input of which is connected to the ground bus , and the control input is connected to the output of the pulse shaper.