SU1206937A1 - Voltage converter - Google Patents

Description

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The invention relates to converter technology and can be used in secondary power sources with a high switching frequency of transistors.

The purpose of the invention is to reduce power losses by speeding up the process of turning on power transistors.

FIG. 1 is a circuit diagram of a voltage converter; in fig. 2 is a time diagram of transformer pulses i in FIG. 3, - the same, current drossel: 1; in fig. 4 - the same as the base current of the transistor.

The converter contains a control transformer 1, the secondary windings of which are connected via resistors 2 to the power transistors

3 and 4. The collectors of transistors 3 and

4 are connected to the primary winding of the power transformer 5, to the secondary winding of which the output rectifier 6 is connected with a capacitive filter 7. Sources 8 of locking voltage through a diode

9 are connected between the collectors of transistors 3 and 4 and their INPUT; chains - common points separated resistors 2 (2 and 2). In series with the secondary windings of the control transformer 1, chokes 10 are connected.

The device works as follows.

The input of the transformer 1 control device is supplied by square symmetrical pulses U / (Fig. 2), the transistor 3 opens and a current flows through it which through the transformer 5 and the converter 6 enters the load and charges the capacitive filter 7. When changing the polarity of the control eg 069372

The transistor 4 is maintained in the closed state by a source of 8 blocking voltage, applied through an absorbable transistor 3.

5 and diode 9. Simultaneously with this process, the process of charging the inductance of the throttle 10 by the current flowing through the circuit and, -2-8-9-3-10-Uj (t, The current through the choke 10 is shown in Fig. 2. The constant rise time of current i is determined by the ratio, and the duration of current flow i by the resorption time of transistor 3. Absorption of minority carriers in the transistor region is effected by an exponentially decaying base current, and the time constant in the base circuit is tg-Lgp / Rs. After dissolving the minority carriers, transistor 3 is closed. are, the source 8 is disconnected from the latch transistor base bias circuit 4. The current of the choke 10, reaching values Ij,

25 rushes into the base transition,

The switching-on forcing and additional clamping of the transistor 4, necessary for providing the maximum charge current of the capacitors of the filter 7, is detected at the stage of turning on the transistor. The base current decreases from the value of I to Ig-occurs with a constant time t chosen by a slightly longer time constant.

JJ of the charge of the capacitors of the filter 7. The shape of the base current of the transistor 4 is acquired in FIG. four.

By choosing the ratio of the resistance values between the divided parts of the resistors 2 (2 and 2), one can obtain the optimal current value 1.1 (Fig. 3) and minimize the power loss when the transistors 3 and 4 are turned on.

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Claims (2)

1. VOLTAGE CONVERTER, comprising power transistors, the collectors of which are connected to the primary winding of the power transformer, an output rectifier with a capacitive filter, a control transformer, the secondary windings of which are connected to the input circuits of the power transformers, which isolate the voltage through the diode to the corresponding input circuit zistors, sources, each of which is between a switching power transistor and a neighboring collector, characterized in that, in order to reduce power losses by means of In the process of switching on the power transistors, inductors are connected in series with the secondary windings of the control transformer. 2. The converter according to π. 1, characterized in that each of these resistors is divided into two parts, to the common point of which is connected a corresponding source of blocking voltage. Figure 1 ί