SU1647803A1 - Push-pull dc-to-ac voltage converter - Google Patents

Abstract

This invention relates to electrical engineering and can be used in secondary power supply sources. The goal is to increase efficiency. The device contains a transformer 1, the windings of which are made in the form of two sections 2,3, located on symmetrical sections of the magnetic circuit. The control unit 17 generates a control voltage for the semiconductor switches 10. 11, switching which leads to the appearance of an alternating voltage on the primary 4, 5 and secondary 6, 7 semi-windings. Implicit scattering inductances between the primary 4, 5 and secondary 6, 7 semi-windings reduce the through-currents in the rectifier diodes 14. 15 and transistor switches 10.11. Additional half windings 8, 9 are needed to reduce the inductive voltage surge on transistor switches 10,11. 1 hp f-ly, 2 ill. 76 v Ё

Description

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The invention relates to electrical engineering and can be used in the sources of secondary power supply systems of radio engineering, automation and computer technology.

The aim of the invention is to increase the efficiency of a push-pull DC / DC converter.

FIG. 1 is a schematic of a two-stroke DC / DC converter; FIG. 2 a converter transformer.

A two-stroke DC / DC converter contains a transformer 1, the windings of which are made in the form of two sections 2 and 3, each of which contains the first 4 v second 5 primary half windings, the first 6 and second 1 secondary half windings and the first 8 and second 9 additional half windings semi-winding, first 10 and second 11 transistor switches, first 12 and second 13 return diodes, two rectifying diodes 14 and 15, filter 16, control block 17.

This technical solution introduces only modal improvements without changing the general principle of operation of a push-pull converter. Modal improvements are due to the introduction of the dispersion inductances that are not clearly present between the primary semi-windings 4 and 5 of sections 2 and 3, between the secondary semi-windings 6 and 7, and also the introduction of a transition inductance between the input and the the output of the transformer 1. In this case, there is a cross-transfer of energy from the primary half winding of one section to the secondary half winding of the other section through a transient inductive spine dissipate.

Let us first consider how the limiting of through currents is carried out, taking into account that transistor switches 10 and 11 are controlled by well-known methods for unregulated and adjustable converters from control unit 17. Suppose that at the beginning of the second half-period of operation of the converter, key 11 is opened, and key 10 despite the presence of a locking signal at its control input remains open for a finite time. The voltage of the converter in this period of time is not short-circuited, but connected to the leakage inductance between the half-windings 4 and 5.

Since during the switch off time of the switch 10 there is no energy transfer from the input to the output of the transformer, the current through the previously open diode 15 and the half winding 7 continues to provide energy to the droplets of the filter 16. After the turn-off time, the switch 10 closes, the polarity of the voltage on all windings of the transformer 1 changes on the opposite to the previous half period. Opens

the diode 14, and the diode 15 for a finite recovery time for the reverse resistance also remains open.

The total voltage of the semi-windings 6 and 7 is applied to the leakage inductance between the half-windings b and 7. When the diode 15 is locked, the operating mode of direct energy transfer to the converter output from the half-winding 5 of section 3 through diode 6 of section 2 and diode 14 begins. This is the accumulation of a portion of the transmitted energy in the cross leakage inductance.

Simultaneously through the half winding 6 in

0 load is also transferred to the part of the energy of the previous half period accumulated in the cross inductance between the half-windings 4 and 9. A minor part of the energy of the previous half-period caused by the non-ideal magnetic coupling between the half-windings 4 and b of section 8 returns to the power source through the additional half-winding 8 and the opening diode 12 when the voltage on

0 half winding 4 reaches its maximum value. The transformation ratio between the half windings 8 and 4 is taken slightly less than one. Accordingly, the additional overvoltage of voltage 5 on transistor 10 does not exceed the value (1.03-1.07) of the input voltage.

Similar processes take place in the next half-period when the key 10 opens, the key 11 closes, the diode 15 opens, followed by closing the diode 14 and transferring energy from the half-winding 4 of section 2 to the half-winding 5 of section 3 through cross inductance

5 in between.

The presence of not clearly pronounced inductances of dispersion ensures continuity or smooth change of the current in the power source in transient conditions.

0 switching power transistors, and a smooth rise and fall of the current in all modes, including when controlled by PWM. This significantly reduces the level of high-frequency frequencies created by switching processes.

From the distinctive features of the operation of the converter, it also follows that the cross inductance of dispersion between the primary and secondary

by means of semi-windings, it helps to reduce current ripple not only in the input circuit, but also at the converter output by accumulating during the working pulse (the open state of the transistor switch in each half-period) of a part of energy with its subsequent transfer to the converter output during the pause time, as is typical for drossels output filter 16.

Consequently, the cross leakage inductance between the primary and secondary semi-windings simultaneously complements the functions of the output filter and contributes to reducing losses from through-currents, increasing reliability efficiency and reducing noise levels. In this case, the transformer t is realized on ordinary serial cores by simply dividing the working section of the magnetic circuit and its windows into two equal symmetrical parts without increasing the size and weight of the transformer.

FIG. 2 shows examples of the placement of sections 2 and 3 on core (a), armor (b) and toroidal (c) types magnetic cores. moreover, the effectiveness of the invention is greatest when using a U-shaped core, where the distance between the centers of the winding sections is greatest.

Claims (2)

Claim 1. A push-pull DC / DC converter with a transformer, the windings of which are made in the form of two sections, on symmetrical sections of the magnetic conductor, each of which consists of primary, secondary and additional semi-windings, the first and second transistor switches, the control terminals of which are connected to the output of the control unit, the first power terminals to the first input terminal, and the second power terminals are connected respectively to the beginning of the first the primary half winding and by the end of the second primary half winding, the free terminals of which are connected to a second input terminal connected to the first terminals of the first and second return diodes, the second terminals of which are connected respectively to the beginning of the first additional half winding and to the end of the second additional half winding, the free terminals of which are attached to the first an input terminal, two rectifying diodes, which form a full-wave rectifier with the first and second secondary half windings, the output terminals of which are connected through a filter with output terminals, characterized in that, in order to increase the efficiency, the first and second secondary half windings are switched on so that current flows for each of the primary semi-windings, a current appears in secondary half winding of the opposite section. 2. The converter according to claim 1, about tl and h a rout, and so that the ratio of the turns of the primary to the additional half windings is selected in the range of 1.03 - 1.07.