Вісники та науково-технічні збірники, журнали
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Item Забезпечення стійкості перетворювачів напруга-струм з комплексним навантаженням(Видавництво Львівської політехніки, 2014) Ю.В. БаланюкЗапропоновано методику визначення стійкості перетворювача напруга-струм, виконаного за схемою підсилювача постійного струму з глибоким зворотним зв’язком за струмом і навантаженим на індуктивність. Наведено аналітичні вирази для визначення запасу стійкості за фазою та амплітудою. Графічно показано вплив опору резистора шунтування індуктивного навантаження на стійкість роботи перетворювача. In this paper, the method of determining the stability of the voltage-to-current converter (VCC) with complex load, which is built on the DC amplifier with a deep negative feedback (NFB) by current. The feedback signal is formed on precise resistor, which is connected in series with an inductive load. The deep feedback and complex load can cause a violation of the stability of the VCC across the whole dynamic range of operation. Additional complexity to ensure stability of the VCC is provided by complex nature of the load. Outside the range of middle frequencies (over 30 kHz) the transfer coefficient is determined by the inductance of load and by the resistor, which forms feedback signal. The feedback factor stops to be a real value and becomes a complex. The phase of NFB signal voltage begins to change and the NFB effect on providing the specified accuracy and on the speed of the current setting in the inductive load is reduced. Upon reaching the large phase shifts in circuit of the VCC amplifier and inductive load at certain frequencies NFB becomes positive, leading to a significant distortion of the output signal and the deterioration of the basic parameters of the VCC, in the worst case, to the self-excitation. It is shown that the stability of VCC is affected by the gain of the amplifier without accounting the NFB influence, depth of feedback and the inductive load time constant tН. Since the gain of the amplifier without accounting the NFB influence and transfer coefficient of the circuit, – inductive load - NFB signal formation resistor, depends on the frequency, the VCC with a load is analyzed as at least the second-order operating system. This system has a tendency to self-excitation and can only be conditionally stable. The analysis of methods for determining the stability of VCC with deep feedback was carried out. The determination of stability criterions of Mikhailov, Routh–Hurwitz and Nyquist was considered on the real Bode diagrams. It was determined that in order to find the stability margin, the most advisable in practice to apply the Nyquist stability criterion in its graph-analytical implementation. The stability of the VCC, which is built using operational amplifiers which are presented by one equivalent RC-circuit, was analyzed. The design method for constructing the total amplitude-frequency characteristic, accounting the parameters of the VCC and inductive load, is given. Two examples of VCC implementation: with low inductance load and with large inductance load, are considered. The analytical expressions for determination of the equivalent frequency poles of the system are presented. There is showed how to choose the shunting resistor to ensure the stability. The dependencies of the amplitude-frequency and phasefrequency characteristics on the shunt resistor of inductive load are illustrated, showing its effect on the stability of the VCC operation, as well as the margin of stability of the phase.Item Визначення часу встановлення струму в індуктивному навантаженні перетворювача напруга-струм при негармонічній дії(Видавництво Львівської політехніки, 2013) Василюк, В. Я.; Шклярський., В. І.The paper presents analysis of problems dealing with the determination of the current setting time in the inductive component of the complex load of Voltage-to-current (VTC) converter under non-harmonic input influence. There is showed the change in the transient response and in the current setting time of the inductor on changing the VTC converter and complex load parameters. Expression to determine the current setting time of complex load of VTC converter at given level of dynamic error is presented. The estimation of dynamic error in determining the current setting time is presented in accordance with the time dependencies of transient responses of current setting in inductive load of VTC converter with complex load’s and VTС’s converters different parameters. The mathematical model of precision VTC converter [1] with deflection system (DS) of cathode-ray tube (CRT) of television scanning optical microscope connected to its output has been designed and is presented as a complete equivalent circuit taking into account the resistance and parasitic capacitance of load. In accordance with the set conditions of raster formation on screen of such CRT, the control of converter is carried out by non-harmonic signal with variable shape, frequency, amplitude and displacement [2]. Precision VTC converter built as parallel circuit with a deep DS’s current feedback, the signal of which is formed on the feedback resistor, which is connected in series with the load, has been studied. To ensure the aperiodic current setting the bypass resistor is connected to the load in parallel. While analyzing this circuit we’re considering that: the static error due to instability of comparison resistors and feedback resistor is equal to zero, the cutoff frequency of VTC converter is higher than the resonant frequency of the load, and the error due to resistance of DS is compensated. The mathematical model allows to carry out a complete theoretical study of precision VTC converter and to get expressions to determine the parameters upon certain conditions: 1) supply voltage of VTC converter is higher than the maximum voltage on the DS during the transition process; 2) amplifier is presented as one inertial circuit with real parameters: unity gain frequency fВ , gain amplifier K0 ; 3) the resistance of DS rL and parasitic capacitance CL are taken into account at analysis; 4) considered that the feedback resistor RЗЗ is non-inductive; 5) the current flowing through the resistor R2 relative to current of feedback resistor is very small and it is neglected. Розроблено математичну модель прецизійного перетворювача напруга-струм (ПНС), навантаженого відхилювальною системою (ВС), яка забезпечує визначення часу встановлення струму у індуктивній складовій навантаження з необхідною точністю при заданій динамічній похибці. Наведені часові залежності встановлення струму у індуктивній складовій при зміні параметрів ПНС та комплексного навантаження.Item Перетворювач напруга-струм як засіб формування струму в комплексному навантаженні(Видавництво Львівської політехніки, 2012) Василюк, В. Я.; Шклярський, В. І.Наведено основні області застосування перетворювачів напруга–струм (ПНС) та вимоги до їх параметрів. Розглянуто характерні особливості реалізації ПНС при комплексному (індуктивно-активному) характері навантаження. Запропоновано класифікацію ПНС відповідно до різних класифікаційних ознак. Визначено подальші шляхи дослідження ПНС з комплексним навантаженням.In this paper is given major areas of application voltage to current(VTC)converters and the requirements their settings. The characteristic features of VTC converters in the comple[ (inductively-active) nature of load. The classification of VTC converters according to different classification criteria to proposed. Defined further ways of learning the VTC converters with a complex load.