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DOI: 10.18413/2518-1092-2019-4-4-0-9

ABOUT PRECISION DIGITAL-ANALOG CONVERTER (PWM-VOLTAGE)

Artem Maximovich Brazhnikov
Aleksandra Maximovna Brazhnikova
Borislav Eduardovich Zaberzhinsky

The article describes the process of developing a high-precision measuring Converter of pulsewidth modulation (PWM) signals into a constant voltage. The review of existing types of converters is given, their advantages and disadvantages are analyzed. The necessity of creating a new Converter is substantiated. The proposed scheme of the device allows it to be used in a number of specific cases, for example, for low-frequency signals (up to single pulses), as well as for PWM with low duty cycle, without loss of accuracy and resolution. The basis is the principle of filling the input pulse with high-frequency pulses of the clock generator, their subsequent calculation and conversion of the number of pulses into voltage by means of a digital-analog Converter with a parallel input (resistive matrix). The article describes in detail the operation of the Converter (block diagram), as well as its schematic diagram, which was tested by means of the software package Multisim. After checking the principles of operation of the Converter, its prototype was assembled. Assembly was carried out from ready chips: counters, registers, elements of standard logic. The description of its operation and characteristics are given, the distinctive features are indicated, including the frequency control of the clock generator, which allows controlling the process of filling the input pulses with the generator counts, regardless of the PWM frequency. This makes it possible to use the transducer in the above cases. In conclusion, the error calculation is given. Among the factors that affect the accuracy of the allocated bit width of the DAC, as well as the maximum frequency of the clock. The main factor affecting the linearity of the transducer – variation of the values of the components in the resistive matrix. The developed scheme of the device is simple, stable, repeatable means of programmable logic integrated circuits (FPGA), which opens up opportunities for its implementation in a variety of designs, which requires high accuracy and speed to convert PWM signal into DC voltage.

Keywords: digital-analog converter, pulse-width modulation, measuring converter, resistive matrix, counters, standard logic chips.
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