A simple powerful switching power supply for powering radio electrical equipment 220 volts 300 watts. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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A simple powerful switching power supply for powering radio electrical equipment 220 volts 300 watts. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Power Supplies

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Often, when assembling some kind of electronic structure, such as: an audio frequency amplifier, automation equipment, devices based on microcontrollers, and much more, we wonder how to power the equipment? Most electronic devices are powered by a constant voltage different from the mains voltage. Recently, more and more often, impulse technology is replacing traditional transformer power supply circuits from everyday life. The gain here is obvious, firstly, it is the saving of winding material, which is not cheap. Secondly, these are the dimensions and weight of the devices, today, with the modern miniaturization of equipment for various purposes, this issue is very relevant, most UPS circuits are quite difficult to assemble and configure and are not available for repetition by novice radio amateurs.

This article provides a diagram of a simple UPS, the development of which was aimed at simplicity of design, good repeatability, the use of improvised material, and ease of assembly and configuration. Despite the simplicity, the UPS has pretty good performance.

Technical specifications

Mains supply voltage: 220 V/50 Hz.
Rated output power: 300W
Maximum output power: up to 500W
Voltage conversion frequency: 30KHz
Secondary rectified voltage varies as needed

Schematic diagram

(click to enlarge)

The principle of operation of the UPS is as follows: the pulses for key control are generated by a master oscillator built on a special driver TL494, the control pulse frequency is 30 kHz. The control pulses from the outputs of the microcircuit are fed in turn to the transistor switches VT1, VT2 of the preliminary pulse shaper for the output power switches. Keys VT1, VT2 are loaded with a control transformer TR1, which generates control pulses for powerful output switches VT3, VT4, the shaper is necessary for galvanic isolation of the gate circuits of the output stage. The UPS is built according to a half-bridge circuit, the midpoint for the half-bridge is created by capacitors C3, C4, which simultaneously serve as a smoothing filter for the supply voltage of the network rectified by the VDS1 diode bridge.

The R7,C8 circuit provides short-term power to the master oscillator and control pulse shaper, for the initial start-up of the UPS, after the capacitor C8 is fully charged, the shaper is powered directly by winding 3 of the TR2 transformer, from which the 12V alternating voltage is removed. The VD2, C6 chain is used to rectify and smooth the voltage supply to the driver. The zener diode VD1 limits the initial start voltage to 12V. The secondary supply voltage for the electronic equipment is removed from winding 3 of the TR2 transformer, rectified by Schottky diodes VD3, VD4 and fed to the smoothing filter C9, C10. If the required supply voltage exceeds 35V, two diodes are switched on in series.

A few words about the design of the UPS: Most of the components are taken from a faulty ATX computer PSU. Namely, this is the TL494 chip, capacitors C9, C10, diode bridge VDS1, capacitors C1, C2, C5, C6, C7, diode VD2, Schottky diodes VD3, VD4, and ferrite cores with frames TR1, TR2.

The UPS itself was structurally assembled in the case of the same disassembled PSU ATX transistors VT3, VT4 installed on radiators with an area of 50 cm / sq.

Rewinding data of transformers TR1,TR2:

TR1, all four windings contain 50 turns of 0.5 mm wire
TR2, Winding 1 is wound with 0.8mm wire 110 turns. Winding 3 contains 12 turns of 0.8mm wire. Winding 2 is wound depending on the required secondary supply voltage and is calculated from the ratio of 1 volt / 2 volts. Since the output is a voltage doubler.

Good luck with your repetition!

Download printed circuit board in Layot format (6 KB)

Author: Artur (Lefty); Publication: cxem.net

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