RU2819373C1 - Universal time-pulse integrating voltage converter with pulse-width modulation function - Google Patents

Abstract

FIELD: precision pulse electronics.

SUBSTANCE: disclosed is a time-pulse integrating voltage converter with a pulse-width modulation function, consisting of four operational amplifiers, on which two voltage repeaters, an integrator and a comparator are implemented, four-channel switch and three inputs, through which two input voltages are connected and an electric jumper may or may not be connected. Four-channel switch is connected to the first input and output of the inverting repeater of the first input voltage and to the second input and output of the inverting repeater of the second input voltage in the input circuits of the comparator and integrator, respectively.

EFFECT: considerable increase in the operating range of variation of input voltages, in which the required linearity of conversion functions, low conversion error, reduced time for adjusting the converter circuit are achieved.

1 cl, 1 dwg

Description

The invention relates to precision pulse electronics and can be used in electronic automatic control and regulation systems, in telecommunication systems and measuring equipment.

Time-pulse voltage converters into rectangular pulse repetition frequency (RPF) are known, also called in electronics controlled pulse generators and pulse-frequency modulators. Time-pulse voltage-to-time converters (PFC) are known, or more precisely, to the time interval (the duration of the pulses or their repetition period).

The circuit design of low-voltage frequency converters and night vision devices, analysis of their conversion functions, metrological characteristics and features of practical use are widely presented in the technical literature [Gutnikov V.S. Integrated electronics in measuring devices. - L.: “Energoatomizdat”, 1988 - 304 pp., p. 256; Aleksenko A.G. and others. Application of precision analog microcircuits. - M.: “Radio and Communications”, 1985. - 304 pp., p. 133; Volovich G.I. Circuitry of analog and analog-to-digital electronic devices. - M.: “Dodeka-XX1”, 2005. - 528 p., p. 199; R. Count. Electronic circuits: 1300 examples. - M.: “Mir”, 1989. - 688 p., p. 600; Fedorkov B.G., Taurus V.A. DAC and ADC microcircuits: operation, parameters, application. - M.: “Energoatomizdat”, 1990. - 320 pp., p. 251; Safinov Sh.S. Analog and analog-digital electronics in automated systems: textbook. Manual in 2 hours. Part 2. - Ufa: Ufimsk. state aviation tech. univ., 2014. - 367 pp., Ch. 1, p. 15].

Known VFCs and NVGs have the disadvantage that they can perform only one type of conversion of the input voltage into one parameter of the output pulse voltage - frequency or time interval (pulse period or duration), completely excluding pulse width modulation.

A known time-pulse universal voltage converter [patent for invention No. 2689805, 05.29.2019, bull. No. 16, MPK-N03K3/13], consisting of an integrator, a comparator, two voltage followers, each of which can function as an inverting or non-inverting voltage follower depending on the state of the comparator, and a four-channel switch that allows the conversion of input voltage to frequency output pulse voltage and time interval (pulse duration or repetition period) with or without performing the arithmetic division operation.

The closest to the declared universal time-pulse integrating voltage converter (hereinafter UVIIP) in circuit design, principle of operation and the achieved result of converting the input voltage is a time-pulse universal integrating voltage converter with a pulse-width modulation function [patent for invention No. 2731601, 04.09.2020 g., bull. No. 25, MPK-N03K 3/13], which differs from the above-mentioned converter in that a third input is introduced into the electrical circuit for connecting an electrical jumper. In this converter, if the jumper is not connected to the third input, then the circuit allows the conversion of the input voltage into the frequency of the output pulse voltage or into a time interval, but if an electrical jumper is connected to the third input, then the converter will perform the function of pulse-width modulation of the input voltage.

The time-pulse voltage converter presented above, which is a prototype of the claimed UVIIP, has a significant drawback, which is the occurrence of nonlinearity in the function of converting the input voltage into frequency, time interval and duty cycle of the output pulse voltage, which reduces the operating range of changes in the input voltage and increases the relative error of the conversion. In laboratory studies of prototypes of these converters, implemented on domestic integrated operational amplifiers and an analog switch, as well as their foreign analogues, the maximum frequency of the output pulse voltage was limited to 4 kHz with a relative reduced conversion error of no more than 0.5%, which cannot be considered acceptable for electronic devices of the type in question.

Mathematical analysis of the sources of error in the conversion of electronic circuits and generalization of the results of laboratory studies of prototype prototypes lead to the conclusion: the electronic circuit of the prototype has two drawbacks.

The first drawback is the influence of the imperfection of the analog switch, which consists in the existence of a residual resistance (10-30 Ohms) of the switched-on channel and a residual current of the switched-off channel (100-500 nA). These electrical parameters of the analog switch eliminate the required operating modes of the two voltage followers on the operational amplifiers.

If the voltage follower is in an inverting state, then the residual resistance of the switched-on channel of the switch is added to the resistance in the inverting input circuit, and the residual current of the switched-off channel of the switch flows through the resistance in the non-inverting input circuit of the operational amplifier. Therefore, the voltage transfer coefficient of the inverting follower K _and will differ from the required value K _and = - 1.

When the voltage follower is in the non-inverting follower mode and the transmission coefficient K _and = 1 is required, the negative feedback resistance in the circuit is not zero, and the residual current of the switched-off channel of the switch flows in the inverting input circuit, so the requirement of K _and = 1 cannot be met in any way .

The considered negative factors, which exclude the required operating modes of two voltage followers in the prototype circuits of the claimed UVIIP, do not allow obtaining the desired high accuracy of voltage conversion into frequency, time interval or duty cycle of the output pulse voltage in the required wide range of changes in the input voltage of the UVIIP.

The second drawback of the prototype's electrical circuit is due to the transient switching processes of the analog switch and the operating modes of two voltage repeaters, the duration and configuration of which affect the linearity of the conversion functions and, therefore, the accuracy of the conversions, and the higher the frequency of the output pulse voltage, the stronger their negative impact.

Time diagrams of the leading and falling edges of the switch output voltage, obtained during laboratory tests of two prototypes of known converters, show that the amplitude of transient processes reaches the level of the switched input voltage, and their duration corresponds to the establishment time of the type of integrated analog switch used (for example, KR590KN7). But the most significant negative factor is that the transients of the output voltage of the switch are modulated by the transients of the voltage followers synchronously switched by the switch.

On the oscillogram, transient processes at the outputs of the voltage followers become almost twice as long and visually represent the sum of the harmonic components that come to the input of the voltage integrator and, which is unacceptable, to the input of the comparator on the operational amplifier without feedback. The comparator compares the first input voltage with the output voltage of the integrator and can switch not when equal to ± _Uin = ± _{Uout. int.} , but erroneously operate during transient processes. Therefore, the duration of the pulses and their repetition period become not stable when the first and second input voltages remain unchanged, but constantly changing, which causes an increase in the error in converting input voltages into frequency, the duration of the pulses, the period and duty cycle of their repetition at the output of the converter, and the greater the more second input voltage of the converter.

The objective of the invention is to expand the areas of electronics in which the use of UVIIP allows reducing the costs of producing electronic automatic control systems for complex multidimensional technical objects, increasing the attractiveness of the subject of the invention for the microelectronics industry, as a universal time-pulse device, suitable and economically feasible for mass production in the form of an integrated microcircuits finally show that time-pulse electronics have not exhausted their capabilities in the emergence of new circuit solutions that make it possible to obtain products with higher metrological and operational characteristics.

The technical result is a significant increase in the operating range of changes in input voltages, in which the required linearity of the conversion functions, low conversion error, and a reduction in the setup time of the converter circuit when preparing it for operation as part of an electronic system are achieved.

The problem is solved and the technical result is achieved in the claimed UVIIP, in which a four-channel switch is connected to the first input and output of the inverting follower of the first input voltage and to the second input and output of the inverting follower of the second input voltage in the input circuits, respectively, of the comparator and integrator, providing static states inverting repeaters of the first and second input voltages.

In fig. Figure 1 shows the electrical circuit of the UVIIP, which consists of operational amplifiers (hereinafter referred to as op-amps) DA1 and DA2, on which inverting repeaters of input voltages U _{input 1} and U _{input 2} are implemented with equal resistances R ₁ = R ₂ and R ₄ = R ₅ . Op-amp DA4 has an inverting integrator, at the input of which the input voltage _Uin.2 or its inverted value _-Uin.2 can act, if the electrical jumper Z is not connected to the third input of the circuit under consideration. Op-amp DA3 implements a comparator that compares the input voltage _Uin.1 or its polarity-inverted value - _Uin.1 with the output voltage of the integrator -U _int. or U _int.

In the UVIIP circuit shown in Fig. 1, the comparator on the op-amp DA3, with equal resistances R ₇ =R ₈ , switches to the opposite (according to the polarity of the output voltage) state when the equality |-U _{input 1} |= U _{int is violated.} by only a few microvolts, which depends on the voltage gain of the type of op-amp used.

It should be noted that the maximum possible frequency of the output pulse voltage UVIIP depends on the speed of the comparator and, to a lesser extent, on the speed of the integrator op-amp DA4, which are normalized by the reference parameter of integrated op-amps - the rate of rise of the output voltage, [V/µs], and does not depend on the speed of the op-amp DA1 and DA2, since they operate in static mode, which fundamentally distinguishes the claimed UVIIP circuit in Fig. 1 from the prototype diagram.

Moreover, when using op-amps with nanoamp input currents, resistors _R3 , _R6 , _R9 and _R11 can be excluded from the UVIIP circuit by connecting the corresponding op-amp inputs to a common bipolar power supply bus.

Let's consider the process of push-pull integration in UVIIP, when the electrical jumper Z is not connected to the third input, integral op-amps that are idealized in their parameters and R ₇ = R ₈ are used, which indicates that the comparator response thresholds are equal to the input voltage + U _{input 1} or -U _{input. 1} .

The first integration cycle, similar to the prototype circuit, is described by the equation:

where T ₁ is the duration of the first beat, - integrator time constant.

In the second integration cycle

where T ₂ is the duration of the second beat.

Solving equations (1) and (2) regarding the durations of integration cycles T ₁ and T ₂ , we obtain:

The durations of negative T ₁ and positive T ₂ in terms of the polarity of the pulses at the output of the comparator at op-amp DA3 are the same, which means the period T = T ₁ + T ₂ or

Comparator output pulse voltage frequency

The bipolar output pulse voltage of the comparator at op-amp DA3, rectified by the pulse diode VD1, is the control signal of the analog switch at op-amp DA5 and is used as a unipolar output pulse voltage UVIIP at Output 1. If a bipolar output voltage is required, then the comparator output voltage at Pin 2 can be used. In these options for obtaining the output voltage of the converter under consideration, the load current is limited by the maximum permissible output current of the type of integrated op-amp DA3 used.

Bipolar transistor VT1 allows you to significantly increase the load capacity of the UVIIP by connecting the load to the collector (Out. 3) or emitter circuit (Out. 4), using it in circuits with an open collector or open emitter, if it is necessary to transmit the output signal of the UVIIP via an electrical line to long distance.

From formulas (3) and (4) it follows:

Firstly, the UVIIP performs input voltage conversion. U _{input 1,} if we consider U _{input 2} unchanged (U _{input 2} = U ₀ ), or the quotient of dividing U _{input 1} / U _{input 2} into the pulse duration or the period of the output pulse voltage;

secondly, UVIIP converts the input voltage _Uin.2 , if we take _Uin.1 fixed ( _Uin.1 = _U0 ), or the quotient of dividing _{Uin.2 /Uin.1} into the frequency of the output pulse voltage.

Now let's consider the process of push-pull integration in the UVIIP, when an electrical jumper Z is connected to the third input.

In this embodiment, using the circuit in Fig. 1, the integrator at op-amp DA4, with equal resistances R ₁₀ =R ₁₁ , integrates the sum or voltage difference _Uin.1 ±Uin.2 _.

The first step of the push-pull integration process is described by the equation:

deciding which relative to the duration of the first measure we get:

In this case, at the first output of the UVIIP the voltage is extremely low, at the second output it is negative of the maximum possible value (almost the supply voltage of the circuit).

In the second cycle, the difference in input voltages _Uin.1 - _Uin.2 is integrated:

and at the first output of the UVIIP there is a high voltage of positive polarity, almost reaching the supply voltage.

From equation (6) we obtain the duration of the second integration cycle:

Period of push-pull integration and output pulse voltage UVIIP

The duty cycle of the output pulses is determined by the ratio of the duration of the positive pulse T ₂ to the period of the output pulse voltage T:

From formula (8) it follows that the UVIIP performs pulse-width modulation of the input voltage _Uin.2 at a fixed input voltage _Uin.1 = U ₀ or the quotient of the division _{Uin.2 /Uin.1} .

So, the claimed universal time-pulse integrating converter converts the input voltage, firstly, into the frequency and time interval (duration and period) of the output pulse voltage, and secondly, into the duty cycle of the output pulses, or all these three types of conversion with simultaneous execution of the arithmetic division operation, without changing the electrical circuit, using the static operating mode of inverting repeaters of two input voltages and four options for connecting the electrical load to the considered converter.

Claims (1)

A universal time-pulse integrating voltage converter with a pulse-width modulation function, consisting of four operational amplifiers, on which two voltage followers, an integrator and a comparator are implemented, a four-channel switch and three inputs, with which two input voltages are connected and can be connected or not connected an electrical jumper, characterized in that the four-channel switch is connected to the first input and output of the inverting follower of the first input voltage and to the second input and output of the inverting follower of the second input voltage in the input circuits, respectively, of the comparator and integrator, providing static states of the inverting repeaters of the first and second input voltages, while the converter is configured to convert the input voltage into frequency and into a time interval when the jumper is disconnected from the third input, and to perform pulse-width modulation of the input voltage when the jumper is connected to the third input, a bipolar transistor is connected to the comparator output through a diode , the collector and emitter of which are connected respectively to the third and fourth outputs of the converter, with the first output connected to the connection point of the diode, transistor and control input of the four-channel switch, and the second output connected to the connection point of the comparator and diode.