SU790295A1 - Analogue-digital converter - Google Patents

Description

one

The invention relates to a pulse technique and, in particular, to analog-to-digital converters with an intermediate conversion into a pulse duration followed by a sub-5 count.

A analog-to-digital converter (ADC) is known, in which the triggered sawtooth generator is connected via a comparator and a trigger with a logic element. And transmitting pulses from the output of the pulse generator to the counting input of the counter, at the outputs of which

The disadvantage of this ADC is the low conversion accuracy due to the nonlinearity of the initial part of the output signal of the generator being started.

A analog-to-digital converter is known, comprising a sawtooth generator, the first and second comparators, a pulse generator, a counter, a source of a reference voltage of 25, a trigger, a first AND element, an OR element and a control unit, the input of a sawtooth signal being connected to the first the output of the control unit, the output and the source of the reference 30

the voltage is connected to the non-inverting input of the first comparator, the inverting input of the second comparator is connected to the input signal bus, the counting input of the counter through the first element I is connected to the output of the pulse generator, which is connected to the second output of the control unit, to the quenching input of the counter and to the first the input element OR, the output connected to the zero input of the trigger / output of which is connected to the second input of the first element AND, and to the input of the control unit, the second. the inputs of both comparators are connected to the output of the sawtooth generator, which triggers the input of the generator, the pulses are connected to the first output of the control unit, and the second trigger serves as a trigger for the sign of the conversion signal 2.

(This ADC eliminates the disadvantage inherent in the previously mentioned converter by using the second comparator. However, the conversion accuracy is also insufficient in it due to the negative effect of the thermal effect inherent in high-speed analog differential comparators of the type that are the most common comparators and in the analog-digital conversion technique. When the ADC operates at the input of the comparator, there is inevitably a significant differential signal heating one of its input transistors and a corresponding change in the residual input voltage of the comparator. This leads to a loss of the non-minal sensitivity of the comparator, to an additional error when performing the conversion, the value of which cannot be taken into account depends on the magnitude of the unknown input signal , i.e., is random .:; The purpose of the invention is to improve the accuracy of the conversion. The goal is achieved by the fact that in the analogue digital converter, A general generator: a sawtooth signal, the first input of which is connected to the first output of the control unit, while the output source of the reference voltage is connected to the first input of the first comparator, and the first input of the second comparator is connected to the input signal bus, and the counting input of the counter the first element I is connected to the output of the impulse generator, which is connected to the reset input with the second output of the control unit, to the counter quench input and to the first input of the OR element, the output connected to the zero input of the trigger, It is connected to the second input of the first element I and to the input of the control unit, the third comparator, the first and second analog switches are entered into it ,,, the analog signal bias unit, the first and second one-oscillators, the first and second pulse shapers, and the second and third AND elements, and the output of the sawtooth generator is connected to. the first inputs of the first and; the second analog switches 1 and through the analog signal bias unit with the first input of the third, comparator, the second input of which is connected to the first input of the second comparator and the second input of the second analog switch, and its output connected to the input of the first single-oscillator, output connected with the third input of the second analog terminal, c. the first input of the second element And through the first driver; 1 pulses - with the second input of this element AND, the third input and output connected respectively to the output of the comparator computer and the second input of the OR element, while the first output of the control unit is connected through the second one-vibrator with the second input of the first analog switch of the reader, with the first input of the third element I, and through the second pulse shaper - with the second input of this element AND, the third input connected to the output of the first comparator, the torus and the output - with the start a pulse input; a single trigger input; the second input of the first comparator is connected to the output of the first analog switch, the third input connected to the output of the reference voltage source, and the second input of the second comparator is connected to the output of the second analog switch. , FIG. 1 is a block diagram of an analog-to-digital converter; FIG. 2 - time diagram of the converter operation. The device contains a sawtooth generator 1, the first and second comparators 2 and 3, the pulse generator 4, the counter 5, the voltage source 6, the trigger 7, the first element AND 8, the element OR 9, the control unit 10, the input signal bus 11, the third i-parator 12, first and second analog switches 13 and 14, block 15 for shifting the analog signal, first and second single-oscillators 16 and 17, first and second formers 18 and 19 impulses SOW, second and third elements And 20 and 21, interface buses 22 control and output information buses 23; FIG. 2, the following designations are given: 24 is the output signal of the generator 1, 25 is the output signal of the block 15, 26 is the signal on the input signal bus, 27 is the start conversion pulse, 28 is the start pulse of the generator 1, 29 is the output signal of the second one-oscillator 17, 30 is the output the signal of the first switch 13, 31 is the output signal of the second driver 19, 32 the output signal of the first comparator 2, 33 is the output signal of the trigger 7, 34 is the output pulses of the first element 8, 35; the output signal of the third comparator 12, 36 is the output signal of the first . single-tube 16, 37 - output signal th switch 14.38 - the output signal of the first form, the world 18.39 - the output signal of the second comparator 3, 40 -. the impulse to end the conversion at the output of the bus 22 of the block 10. The device operates as follows. When an external pulse 27 starts to convert to the input of the bus 22 of the block, 10, the control generates a signal of the initial state, which is fed to the reset input of the generator 4, to the blanking input of the counter: Nca 5 and to the zero input of the trigger 7 via element 9, impulse 28 along which generator 1 generates a sawtooth signal 24. This signal passes through switch 13 to input cc 1parator 2, since impulse 28 also triggers a one-oscillator 17, which switches over the signal; 1H 13 disconnects the inverter; the input of comparator 2 from the output of the source 6 of the reference voltage and connects it to the output of the generator 1. The comparator 2 produces signals 32 when the signal 24 exceeds the level of the reference voltage. Emissions in signal 30 from transients in switch 13 can cause a false comparator 2 (first pulse 32) to fail. Therefore, with the help of the imager 19, generating signal. .nale 31 of gating, and element 21 this false triggering is prohibited. Starting the generator 4 of the pulses and the trigger 7 takes place only from the second pulse of the signals 32, after which the counting of pulses in the counter begins; ke 5. The end of counting of the pulses is carried out comparator 3. In this case, its inclusion in the comparison mode of signals 24 and 26 occurs using the switch .14, one-shot 16 and comparator 12. The comparator continuously compares signals 26 and 25, the last of which is formed from the signal 24 using block 15, and from A. Equality produces a signal 35, This: the signal triggers the one-shot 16, the output signal 36 from which switches 14, which disconnects the non-inverting input of the comparator 3 from the bus 11 and connects it to the output of the saw-tooth generator 1. the converter is operated in the same way as for signal 30, but with the help of shaper 18 and element 20 (signals-38,39). At the output signal of element I 20, trigger 7 of the mouth is cast into the zero state, counting pulses in the counter 5 end The control unit 10 generates a conversion End impulse which removes the result of the conversion from the output lines 23.

Thus, comparators 2 and 3, which determine the accuracy of converting the input analog signal to a code, are included in the comparison mode of signals 26 and 24 only for short intervals of time in accordance with signals 29 and 36, the rest of their inversion, hand and non-inverting inputs are shorted and no differential input signals. Such control of the operation of the converter allows the main measuring comparators 2 and 3 to be modeled with practically no significant differential signal, causing a loss of sensitivity from the thermal differential effect, and thereby increase the accuracy of the transducer

Claims (2)

1.. Gitis E.I. Information converters for electronic digital computing devices, m, energy, -1975, p. 292, fig. 7-5 in. 2. Transformation of information in analog-digital computing devices and systems. Ed. G.M.Petrova. M., Mechanical Engineering 1973, p. 234, fig. 90 / prototype). S -HT Jul t i t i  i Jinim t and: fPue.2