Calculation of pulse voltage stabilizer

This scientific article is devoted to one of the priority issues in electronics, namely the implementation of the engineering task of designing a power source. In my case, according to the terms of reference, which includes: the main parameters of the network, efficiency, a structural electrical circuit of a switching power supply was developed. In the process, the main functional units (blocks) were calculated and the choice of radio components from which they were built on the basis of: current values, reverse voltage, gain, operating frequency and other parameters of diodes, transistors, integrated circuits, Zener diodes, operational amplifiers was justified. In the “Methods” section, calculations will be made for the device blocks: a network rectifier, a push-pull transformer converter, a pre-amplifier circuit with a transformer input, an error signal comparison and amplification circuit, a sawtooth voltage generator, and a secondary power source. The information presented in the text is recommended to a narrow circle of specialists, priority in the field of power electronics, as well as in the field of communication systems.


Introduction
Switching voltage stabilizer -a voltage regulator in which the regulating element is in the cutoff mode (R ) or under saturation (R ), hence can be considered as the key [1,121]. Smooth change of voltage occurs due to the presence of integrating elements: the voltage rises as you accumulate them energy and decreases its impact in the load. This mode reduces energy loss and improves weight and overall dimensions, however, has its own characteristics.
Essential elements of a switching power supply are: integrator, which voltage can not change instantly, but gradually increases according to the accumulation of energy and then slowly drops as it returns to the load (for example a capacitor, to which included some non-zero resistance, which can be, for example, the internal resistance of the power source) and a device able to change the resistance to the passage of current from minimum to maximum and Vice versa.

Methods
This simulation was carried out at the Department of Electronics and Communications. During the calculations, the Mathcad program was used, as well as the development environment of electronic circuits Multisim.

Materials
Has been provided by the technical specification (requirements) regarding the network conditions for which it is planned to produce the product. Input the following: Power supply voltage: Ups = 36 V; the Relative change in supply voltage: δUps = ± 20 V; Frequency mains current: F = 400 Hz; Type of mains supply: three phase with a "0" output star; Diagram of the network rectifier: three-phase half-wave; load Voltage: U load = 12 V; load Current max: I l max = 5 A; load Current min: I l min = 1 A; ambient Temperature: t = + 50 C; ripple Factor: Kr = 1.5 %; The switching frequency of the Converter: fs = 25 kHz; Diagram of converters: push-pull; efficiency: η = 92 %.

The calculation of the network rectifier
Depending on the number of phases supply rectification circuit may be a three-phase bridge, three phase halfwave, single-phase bridge.
In (Fig.1) shows a diagram of a network rectifier "three phase half-wave rectified". Calculate the main parameters: The average value of the rectified voltage for threephase half-wave circuits:

Calculation of transformer push-pull converter
In this popular scheme (Figure 2), the performance is a combination of electric energy conversion and its regulation through pulse width modulation. Characteristic for them is the presence of a relatively strong smoothing LC filter [2,63].
In half-bridge scheme of transformer push-pull converter, when the transistor VT1 is opened at time γ T/2, and VT2 is closed, energy transfer occurs from capacitor C1 through a transformer T to the cumulative LC choke and the load [3,51]. At the same time, the capacitance C2 is charged through the circuit: +U0, U1 winding, the capacitance C2 and -U0. In the next half cycle the process repeats: the S2 is open, C1 is charged. During the pause, the filter capacitor C is discharged to the load through the diode VD5. Capacitance C1, C2 form a capacitive divider.
The fill factor of the pulse: γ max = 0.7 The output voltage of an RF rectifier: The voltage at the secondary winding of the transformer: The capacity of the smoothing filter: When K r = 2%, : Taken on a number e24: load = 50 µ . Average current of the diode VD5 and its voltage: The average value of the currents and reverse voltage for diodes HF bridge [4]: As the diode bridge is used KD213A with the following parameters:

The calculation scheme of the pre-amplifier with transformer input
In (Fig.3) shows a diagram of a pre-amp.
Balanced resistance is needed to limit the base current of the power transistor of the Converter (after replacing the transistor) due to the variation of parameters h21e, [5]. Balanced impedance:  -voltage logical units on the I ps output of the logical element "and" [6,124].

The calculation of the comparison circuit and the gain error signal
In (Fig.4) shows a diagram of the circuit built on the operational amplifier.

The calculation diagram of the sawtooth generator
The sawtooth generators find wide application in automation, television, communications technology, measurement technology, power supplies and other applications of electronics [8,19]. Most often performed with an external control. The duration of the stroke is determined by the duration of the external control pulse of a rectangular shape [9]. If necessary, you can create generators running in sync mode or the oscillatory modex [10].
In the simplest case, when not required high linearity of the working area of the output voltage, they are executed according to the scheme of integrating RCcircuit with the reset of the charge during the return stroke of the saw. The formation of a sawtooth voltage based on the alternation in time of the processes of charge and discharge of the capacitor. The function of the element, creating a circuit to quickly discharge capacitance, performs a transistor in a key mode. Discharge of the capacitor and maintaining the voltage close to zero, occurs in the interval tp input signal when the transistor is in saturation (fully open). Linearlyvarying voltage in the interval of the stroke is formed when the transistor is closed (nonconductive state).
In (Fig.5) shows a schematic of the sawtooth generator. The value of the voltage of the generator is chosen equal to: U g = 3 V.
The current value of the capacitor equal to: I pow.s = 1 The calculation of the resistance of drain circuit:

Results
As a result, the circuit was simulated and substantially improved in the Multisim program using a separate power source for the control device, which allows controlling the processes occurring both in the network and in the load, regardless of the state of the power unit (RL = 0 or RL = ∞) [11], which simplifies the task of building a reliable control device. Using the obtained calculations, it is planned to make a test model of the device. The results of this testing will be described in a future article.

Discussion
In this section, I want to discuss the merits of a switching voltage regulator relative to a linear regulator. Firstly, it has less energy loss for heating the regulating element, which increases the efficiency of the stabilizer and allows the use of a regulating element of lower power, and a radiator of smaller sizes and weights. You can also note a high efficiency, especially when working in a wide range of input voltages [12,137]; small dimensions and mass (high specific power); fundamental possibility of galvanic isolation of input and output circuits.

Conclusion
Today, the scope of application of such devices has decreased in connection with reduction of power supply sources with transformerless input. Nevertheless, the use of switching regulators in a number of cases, it is economically more profitable than any other DC-DC Converter [13,202].
In this paper we discuss the main provisions for the design of power supplies and electronic equipment. When developing a supply of funds was received for construction of circuits of power. Required the estimated coefficient characterizing their performance [14,47]. On the technical task [15,97] was calculated switching voltage regulator, developed in the software Multisim that will be done in further studies.