SU1365311A1 - D.c.voltage converter - Google Patents

Abstract

The invention relates to a converter technique. The goal is to increase reliability by eliminating the autogeneration mode when the external control signal is turned off. In the absence of a control signal, the positive feedback is turned off, ensuring that the open power transistor is kept open, and the latter is closed. The feedback supporting the turn-off signal on the power transistor is not disconnected, since it is connected not through transistors, but through diodes. In this case, both power transistors are locked and the converter will not be able to switch to the natural frequency. 1 il.

Description

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The invention relates to converter equipment and can be used in automation devices and in secondary power sources.

The purpose of the invention is to increase reliability by eliminating the autogeneration mode when external excitation signals are disconnected.

The drawing shows the scheme of the proposed Converter.

The converter consists of an external excitation transformer 1, to the primary winding 2 of which a control signal is supplied, and the secondary windings 3 and 4 are connected via limiting resistors 5 and 6 to the control electrodes of the power transistors 7 and 8 whose collector-emitter junction is dioded by diodes 9 and 10, and the collectors are connected to the primary winding 11 of the output transformer 12, the secondary winding 13 of which is connected to the output terminals 14.

Additional windings 15 and 16 of the output transformer through the auxiliary transistors 17 and 18 are connected to the first terminals with the bases of the power transistors 7 and 8, respectively.

The other ends of the additional windings through the limiting resistors 19 and 20 are connected to the emitters of the power transistors 7 and 8,

Auxiliary transistors 17 and 18 are bounded by diodes 21 and 22, the cathodes of which are connected to their collectors. The auxiliary transistor bases through limiting resistors 23 and 24 are connected to the secondary windings of external excitation, the limiting resistors of the power transistors are shunted by forming capacitors 25 and 26.

The inverter works as follows.

In steady-state mode with voltage polarity (indicated without side) on the secondary windings 3 and 4 of the transformer 1 external excitation and on the additional windings 15 and 16 of the output transformer 12, the power transistor 7 is open, and the power transistor 8 is closed, the additional transistor 17 is open , and the additional transistor 18 is closed. Positive feedback from add112

The main winding 15 through the open additional -Transistor 17 enters the base of the power transistor 7, keeping it open. The positive feedback signal from the additional winding 16 through the diode 22 is fed to the base of the power transistor 8, keeping it in the closed state. When the voltage polarity changes (indicated in brackets) on the secondary windings 3 and 4 of the transformer 1 external excitation, through the capacitance capacitors 25 and 26 and the limiting resistors 5 and 6, the control signals arrive at the bases of the power transistors 7 and 8. The power switches the transistors, the transistor 7 is closed, and the transistor 8 is opened. The polarity of the voltage on the additional windings 15 and 16 of the output transformer 12 is changed. A positive feedback signal keeps the Viv transistor open in the open state — transistor 7.

In the absence of a control signal on the winding 2 of the transformer 1 of the external excitation, the positive feedback is disconnected, ensuring that the open power transistor is kept open, and the transistor is closed. The reverse positive link, which maintains the closed state of the closed transistor, is not disconnected, since it is connected not through transistors, but through diodes. Therefore, both power transistors will be closed and the converter will not be able to switch to the natural frequency when the control signal is turned off.

Thus, the circuit, when the external excitation signal is disconnected, ensures the disconnection of the positive feedback that causes the self-oscillating mode of the converter at the natural frequency.

Claims (1)

Invention Formula A constant voltage converter containing reverse transistor-shorted power transistors, one of whose power electrodes are connected to the primary winding of the output Transformer containing additional secondary windings3136531 ki, some of the outputs of which are connected to the second power electrodes of the power transistors through limiting resistors, an external excitation transformer whose secondary windings are connected to the inputs of the power transistors through limiting resistors, with the aim of increasing reliability Q exclusion of the autogeneration mode when the external excitation signal is disconnected, between the bases 14 power transistors and the second pins of the secondary secondary output current transformer include auxiliary transistors, the emitters of which are connected to the bases of the power transistors, and the bases through limiting resistors to the secondary windings of the external excitation transformer, and the auxiliary transistors are bridged by diodes whose cathodes are connected to their collectors. / "/ R2