SU1739463A1 - Transistorized inverter - Google Patents

Abstract

Usage: conversion post, voltage in AC. voltage for secondary power systems. The essence of the invention: power transistors 1 and 2 are switched by breaking the emitter circuit using additional transistors 3 and 4. Locking of the power transistor 1 (2) occurs through the collector-base transition through the open auxiliary transistor 18 (19) and diode 22 (23). Winding 29.30 auxiliary transformer 28

Description

cl

WITH

vi co che o co

in conjunction with the windings 9 and 10 of the control transformer 11, they provide protection against through currents when switching power transistors 1 and 2 by locking the device. The invention relates to electrical engineering and can be used in secondary power supply systems and automation.

A voltage converter is known that contains in each arm a main transistor, the control junction of which is connected through the base resistor to the control winding of the control unit and connected to the power circuit of the auxiliary transistor connected to the auxiliary JADD circuit. To eliminate current surges in a given converter, its power transistors must be controlled by two-pole pulses with a pause at zero, the duration of which must exceed the recovery time of an excess charge in the base region of the closing transistor.

However, in the known technical solution, there are conditions for the occurrence of a secondary breakdown when the power transistors are locked, which reduce the reliability of the converter.

Emitter-switched converters are also known, in which an additional transistor is included in the emitter circuit of each power transistor to ensure operation at higher switching frequencies, and a limiting charge-accumulating diode is included in the base circuit of the power transistor. In the known technical solution, the power transistors are alternately in boundary mode due to the limiting of the base voltage using charge-accumulating diodes, which, in combination with the emitter control, reduces the turn-off time of the power transistor.

However, in a known inverter, there are conditions for the flow of through currents through the power transistors due to the absence of a delay to unlock the previously locked transistor for the time required to completely lock the previously unlocked transistor, which does not have a current in its collector circuit. The presence of through-currents with a high filling factor of the control pulses due to the finite resorption time of the excess charge in the limiting diodes with accumulation of charge, the recharge time and capacitance of the collector additional transistors 3 and 4 through the diodes 31, 32 at the stage of absorption of minority carriers in the base power transistors of the opposite shoulder. 1 il.

Diodes of power transistors and diode capacitances with charge accumulation increase dynamic losses and reduce reliability. The closest technical

The essence of the invention is a transistor inverter containing control transformers connected to the inputs of a push-pull power amplifier, auxiliary transformers, the windings of each of which are connected to one of the pairs of adjacent-series-connected transformer bridge and valve element, each additional transformer having an additional

winding, the collector of each of these transistors is connected to the emitter through the back-connected valve element and one winding of the auxiliary transformer connected in series with it, and the control transition is shunted by the other winding of the auxiliary transformer and valve element connected in the forward direction, and sequentially with

An additional winding of the control unit is connected to the valve element and another winding of the auxiliary transformer that shunts the emitter junction. A disadvantage of the known inverter is that when locking the power transistors, there are conditions for the formation of local overloads in the base region. These overloads contribute to the development of secondary breakdown, which reduces

inverter reliability.

The purpose of the invention is to increase reliability by eliminating local overloads of the base area when locking a previously open power transistor while simultaneously ensuring the elimination of through currents through power transistors by automatically delaying the unlocking of one of them by the time required to lock the other, which expands the area

safe operation when turning off the power transistors.

This goal is achieved by the fact that in a transistor inverter containing two capacitors and two controllable switches,

half bridge connected, control transformer with two secondary windings, each of which has

an intermediate tap and an auxiliary transformer with two primary and two secondary windings; the first output of each secondary winding of the control transformer is connected to the first output of the first resistor, the second output of which is connected through the first diode connected in series and the corresponding primary winding of the auxiliary transformer transformer, and each secondary winding of the auxiliary transformer is connected in series with a second diode To form an interlocking chain, an additional transistor is inserted into the emitter circuit of each power transistor, the base of which is connected via a second resistor to the second output of the first resistor and connected to the emitter of an additional transistor connected to the secondary winding of the control transformer via the base of the power transistor is connected through a series-connected fifth diode and a third transistor with the first terminal of the first resistor, counter-parallel A base-emitter junction of an introduced auxiliary transistor is connected to the diode, whose collector is connected to the emitter of the additional transistor through the sixth diode, and a blocking chain is connected in parallel with the sixth diode.

New in the proposed inverter is the introduction of additional transistors, power electrodes connected to the emitters of the power transistors, and bases through a chain of series-connected resistors connected to one of the control transformer windings connected also through resistors to the bases of the auxiliary transistors whose emitters are connected to the bases power transistors, and collectors through the first diodes to the emitters of additional transistors, and through the second diodes to the same conclusions of the first windings of the auxiliary transformer, the other outputs of which are connected to the emitters of additional transistors, the base-emitter junctions of the auxiliary transistors are dioded by diodes, and the base-emitter junctions of the additional transistors are shunted by two diodes each. The connection point of the two resistors in the base circuit of each additional transistor is connected via diodes to the first terminals

the second windings of the auxiliary transformer, the second terminals of which are connected to the other extreme leads of the control transformer windings, the taps from which are connected to the emitters of the additional transistors.

In addition, the power transistors are locked through open auxiliary transistors while simultaneously breaking the emitter circuits of the power transistors, which ensures a safer operating mode of the power transistors without overloading the circuits of their bases, which increases the reliability of the circuit, and

5, the locking time of one power transistor is provided by blocking the unlocking of the other transistor, which eliminates the through currents through the power transistors. At the same time, the switching off of transistors and the locking process are accompanied by overloads in the base areas, which reduces its reliability.

The drawing shows an electrical transistor inverter circuit.

5 The transistor inverter contains power transistors 1 and 2, the emitters of which are connected to the collectors of transistors 3 and 4, the collector of transistor 1 being connected to the first input terminal, and the emitter

0 transistor 4 - with the second input terminal, the emitter of transistor 3 is connected to the collector of transistor 2 and the first terminal of the winding 5 of the output transformer 6, the second terminal of which is connected to the middle point of the chain of series-connected capacitors 7 and 8, the outermost terminals of which are connected to the first and the second input pin, respectively. The windings 9 and 10 of the transformer 11 of the control unit are connected to one of their extreme leads via chains of pair-wise-connected resistors 12 and 13, 14 and 15 to the bases of additional transistors 3 and 4, respectively, as well as

5 through resistors 16 and 17 to the bases of the auxiliary transistors 18 and 19, the emitters of which are connected respectively to the bases of the power transistors 1 and 2. The taps of the windings 9 and 10 of the transformer 11 are connected to

0 emitters of transistors 3 and 4, respectively. Base-to-emitter junctions of transistors 18 and 19 are shunted in the forward direction by diodes 20 and 21. The collectors of transistors 18 and 19 are connected via diodes 22

5 and 23 to the emitters of transistors 3 and 4, respectively, and through diodes 24 and 25 to one of the terminals of the windings 26 and 27 of the auxiliary transformer 28, the other terminals of which are connected to the emitters of transistors 3 and 4, respectively.

The windings 9 and 10 of the control transformer 11 are connected to one of the terminals of the windings 29 and 30 of the transformer 28, the other terminals of which are connected via diodes 31 and 32 to the connection points of resistors 12 13 and 14, 15, respectively. Base-emitter junctions of transistors 3 and 4 are shunted by reverse-connected diodes 33, 34 and 35, 36, respectively. A load 38 is connected to the secondary winding 37 of the output transformer 6.

Transistor inverter operates as follows.

The bases of transistors 1, 3 and 2, 4 receive the voltage of control transformer 11, alternately opening transistors 1 and 3 and closing 2 and 4 and vice versa. Suppose, at steady-state times, a voltage exists on the windings of transformer 11, the polarity of which is indicated without brackets. The transistors of the upper arm 1 and 3 of the half-bridge circuit are in the open state: the transistor 1 is open through the resistor 16 and the diode 20 is in the conducting state, and the transistor 3 is open through a chain of series-connected resistors 12 and 13. The transistor 18 is locked the voltage falling on the conducting diode 20, applied in the opposite direction, and has no effect, the diodes 33 and 34 are also in a non-conductive state. The current through the diode 31 has a very small value determined by the magnetizing current of the winding 29 of the transformer 28 and has almost no effect on the base current of the transistor 3. The transistors 2 and 4 of the lower arm of the half-bridge circuit are closed in the steady mode: the transistor 4 is closed through resistors 14 and 15 negative voltage across the resistor 17 and the shifted base-to-emitter junction of the transistor 19. The diode 23 is also in a non-conducting state, as is diode 25. The non-conducting state of diode 25 is due to the fact that the ratio of the number of turns of winding to 29 and 30 with respect to the winding turns numbers 26 and 27 is selected such that the emf induced in the windings 27 and 26 does not exceed the absolute value of the emf between the taps and the upper terminals of the windings 10 of the transformer 9 and 11

lUg-il lUio-il U26 (

R13

R12 + Ri3

-) + 0.8

W26 W2g

U27

 (Ulo-2 + Uio-i

R15 HQ81 W27

Ri4-bRi5 J W3o

where Ug-1, Uio-i are the voltages between the upper terminals and the taps of the windings 9 and 10 of the transformer 11;

Ug-2, U10-2 are the voltages between the taps and lower terminals of the windings 9 and 10 of the transformer 11;

L / 2b - L / zo - the number of turns of the windings 26 - 30 transformer 28;

Ri2 Ris - Resistors

12-15;

U26, U27 are the voltages across the windings 26 and 27 of the transformer 28.

In addition, the numbers of turns of the windings 29 and 30 are chosen such that the core

transformer 28 under all conditions of over-, magnetization in a linear mode over a particular cycle without entering the saturation region, i.e. working induction in the core should be less than saturation induction, despite the asymmetric mode of magnetization reversal, which can be achieved, for example, using an air gap or using a core with a high saturation induction value (for example

from molybdenum permallo). Diode 32 is in a non-conducting state because the negative voltage at its anode, Ua32, exceeds in magnitude the negative voltage at the cathode UK32 (relative to the emitter of transistor 4).

R15

--Ua32 (U10-1 Rl5

U35 +

35

+ U36) l i -UK32 | I- (U30-U10-2) 1

HU30-U9-2) l h U9-2 + Ug-l

R13

- f

Ri2 + ri3

+ Us63-Ug-2 I 1 -Ug-1

Ris

Ri2 + ris

iebz

0.8;

since Uzs + U34 1.4 Ubez

Ri2 Rn; Ris ris

where Uzz - Use - voltage drops on conductive diodes 33 - 36;

USD voltage across the winding 30 of the transformer 28;

ibaz - voltage drop across the emitter junction of an open transistor 3, (all silicon diodes used, with a voltage drop in the conducting state of about 0.7 V).

In the next cycle, the polarity of the voltages on the windings of the transformer 11 is reversed (polarities in brackets). The faster transistor 3 closes before the transistor 1 through resistors 12 and 13 and breaks the emitter circuit of transistor 1. Diodes 33 and 34 go to a conducting state and limit the amount of reverse voltage applied to the emitter junction of transistor 3. Diode 20 is locked, and the transistor 18 is opened negative with respect to its emitter voltage, and the base of the transistor 1 is connected through the power electrodes of the open transistor 18 and the diode 22 to the midpoint of the successively connected circuits ican half-bridge circuit. Transistor 1 is forcedly locked through its base-collector junction and conductive transistor 18, and due to the broken emitter circuit of transistor 1, the locking process occurs in a safe mode, eliminating the secondary breakdown. Transistor 2 through the resistor 17 and the conductive diode 21 is applied unlocking voltage, however, it remains in the locked state until the transistor 1 is completely locked, since the locking voltage is applied to the transistor 4 relative to the emitter from the bottom relative to the tap of the winding 10 of the transistor 11 and the conductive diode 32. In this case, the voltage drop on the winding 30 of the transformer 28 turns out to be insignificant because the winding 26 of this transformer is shunted through the conductive diode 24, the open transistor 18 and the conductive diode 22. After the completion of the transient process, the locking of the transistor 1 closes the diodes 24 and 22, thereby removing the bypass winding 26 of the transformer 28, the voltage drop across the winding 30 of this transformer increases, the current through the winding is determined only by the magnetisation current, i.e. significantly decreases in magnitude, so diode 32 ceases to have a shunt effect, transistor 4 opens through resistors 14 and 15, and with it opens power transistor 2. In the next half-period, the processes proceed similarly: transition of the transistor 2 is bounded by the winding 27 of the transformer 28; therefore, the base circuit of the transistor 3 is blocked by locking voltage of the lower part of the winding 9 through the diode 31, which prevents It flows through currents through power transistors. When choosing diodes 22 and 23 as diodes with a small voltage drop in the conducting state (for example, Schottky barriers), the blocking of unlocking the previously locked power transistor 1 or 2 occurs earlier than the locking of transistors 3 or 4, which prevents the flow of through currents.

Thus, providing forced locking in the safe mode of transistors 1 and 2 by breaking the circuits of their emitters while at the same time eliminating the flow of through currents during the time of their locking allows increasing the reliability of the transistor inverter.

Claims (1)

Claims of the Invention A transistor inverter comprising two capacitors and two controllable switches connected in a half-bridge circuit, a control transformer with two secondary windings, each of which has an intermediate tap and an auxiliary transformer with two primary and two secondary windings, and to the first output of each secondary the control transformer winding is connected by the first output of the first resistor, the second output of which is connected through the first diode connected in series and the corresponding primary circuit The auxiliary transformer is connected to the second output of the secondary winding of the control transformer, and each secondary winding of the auxiliary transformer is connected in series with the second diode, forming a blocking chain, which in order to increase reliability by expanding the area of safe operation when the power transistors are turned off, each key is made in the form according to a series-connected power transistor and an additional transistor, the base of which is through the second The resistor is connected to the second output of the first resistor and through the third and fourth diodes connected in series with the emitter of the additional transistor connected to the secondary winding of the control transformer, the base of the power transistor through the serially connected fifth diode and the third transistor connected to the first output of the first resistor parallel to the p diode, a base-emitter junction of an auxiliary transistor is included, the collector of which is connected to the emitter through the sixth diode tion of the transistor and a diode in parallel to the sixth included a blocking chain.