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5ТЕХНИЧЕСКИЕ НАУКИ (TECHNICAL SCIENCES) УДК 621-317.7; 621-319
Kerimzade G.S.
Associate Professor of the department "Electromechanics" of Azerbaijan State University of Oil and Industry (Baku, Azerbaijan)
Veliyeva T.B.
2-nd year Master of the department "Electromechanics" of Azerbaijan State University of Oil and Industry (Baku, Azerbaijan)
DEPENDENCES OF VOLTAGE RATIO ON CONVERSION STAGES FOR PULSED VOLTAGE REGULATOR
Abstract: an integral part of modern electronic equipment, the characteristics of which are largely determined by the stability of supply voltages, are integrated voltage stabilizers. Due to the intensive development of technology in a short period of time, the circuitry of integrated voltage stabilizers has gone from simple linear stabilizers to powerful universal pulse devices with a small number of outputs and an efficiency of up to 97%. A device that invariably maintains voltage at a load with a certain accuracy is usually a closed-loop automatic voltage control system. In this system, the output voltage is equal to or proportional to a stable voltage reference generatedfrom a dedicated voltage reference. Such types of stabilizers include a regulating element (transistor) connected in series or in parallel to the load, operating as an active (continuous) linear stabilizer, or continuous regulation, as well as a key (pulse) mode (pulse or key stabilizer).
Keywords: pulse, voltage stabilizer, reference voltage source, control system, control signal, dependence, ratio, device, input voltage, output voltage.
Switching voltage stabilizer - automatic control system. For the control loop, the set parameter is the reference voltage compared with the output voltage of the
stabilizer [1-6]. Depending on the discrepancy signal, the control device changes the ratio of the periods of the closed and open positions. According to the block diagrams, three functional units should be noted: a key, an energy storage device (sometimes called a filter) and a control circuit. The key and energy storage make up the power part of the voltage stabilizer, and with the control circuit they create a control loop. According to the type of control circuit, there are three schemes (with Schmidt trigger, pulse width modulation, pulse frequency modulation). With this control method, the pulse that opens the key is characterized by a constant period, and the pulse frequency depends on the signal of the mismatch between the reference and output voltages. With an increase in the load current or a decrease in the input voltage, the frequency [3-5] increases. Key control, for example, can be carried out by means of a monostable multivibrator. Usually, according to the circuit of the power section, switching regulators are divided into: step-down, step-up and inverting.
The efficiency of linear switching voltage regulators depends on the ratio of input UIN and output voltage UOUT, assuming that the current they consume is small and efficiency = UOUT./UIN. In most cases, when using linear switching stabilizers, the efficiency value is not significant and is 30% or less. In particular, the use of linear switching regulators with a large difference between the input and output voltages is unacceptable; and it should also be noted that all linear switching regulators are step-down, that is, UOUT. they are always less than UIN. When comparing switching voltage regulators with linear ones, they have more advantages. Their efficiency without comparison is large, since the key of the used regulated transistor, according to the mode of operation, its average dissipation power is small than in linear stabilizers. In most cases, this makes it possible to exclude the use of conductors with low thermal losses or reduce their overall dimensions. In addition, along with step-down operating mode of the input voltage (Step-Down), switching voltage regulators also work with step-up (Step-Up) and inverting (Inverting) modes.
When using a choke with one winding in step-down, step-up and inverting circuits, the highest efficiency of the converter is in the range: 0.1 < UiN , UOUT <
10. If the input voltage differs from the input voltage by more than 10 times (fig.1) [3], then the period of one stage of the transformation (ton or toff) is much less than the others:
U OUT U1N
¿on + toff
At the same time, the regulation and filtering of the output voltage becomes more complicated, since current fluctuations increase at small periods ton or toff, and as a result, this leads to a significant decrease in efficiency and makes it physically impossible to implement this mode (the required period ton or toff may be less than the turn-on time / switching off the semiconductor component).
Fig. 1 Dependences of ratios of input, output voltages
f и ^
UOUT
V U iN J
f t Л
1 ON tr
on from the ratios of the periods of the stage V"OFF J
t
on
Therefore, with a large difference between the input and output voltages, an autotransformer connection of chokes is used, so that the transistor or diode is connected to part of the winding [7-10].
Conclusion
Integral pulse voltage stabilizers are devices that express automatic regulation of the output parameter, that is, when the input voltage and output current change within the given limits, they provide voltage to the load. Unlike a parametric stabilizer, such stabilizers are distinguished by high output currents, low output resistances, high stabilization coefficients, and are widely used in modern electronic devices and devices (for example, a computer, telephone, walkie-talkies, etc.). The basis of the control system of pulse stabilizers in order to determine the technical result is the method by means of pulse-frequency modulation of inverter control signals. The peculiarity of this method is measuring the value of the stabilized voltage directly in the load circuit, digitally storing it in the memory of the microcontroller, then rectifying the output parameter and smoothing. The measured value of the stabilized parameter is compared with the required value by means of an amplifier, and is determined in the microcontroller using the installed digital-to-analog converter.
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