SU1636973A1 - Dc 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 reliability by reducing the reverse voltage of the base-emitter switching transistors. The device contains a transformer 1, switching transistors 2, 3 with limiting resistors 4, 5 and boosting diodes 6, 7, starting diode 10, transistor 12 and resistor 13 switching commutator 18. After starting the converter using starting transistors 12 and resistor 13 transistors 2 and 3 is determined by the saturation time of the switching throttle 13. To reduce the reverse voltage, the base-emitter of the switching transistors 2, 3 has a second capacitor 15 and additional diodes 16,17, through which ness inductive ejection voltage on the commutating reactor 18 and feedback windings 8, 9 with 1 seq yl

Description

The invention relates to electrical engineering and can be used in sources of secondary power supply systems of radio engineering, automation and computer technology. 5

The aim of the invention is to increase the efficiency and reliability by saving the energy of the primary source for controlling the starting circuit and reducing the reverse voltage base - emitter of switching transistors of the DC / DC converter.

The drawing shows a diagram of the Converter.

The DC / DC converter 15 contains a transformer 1, switching transistors 2 and 3, the bases of which are connected through limiting resistors 4 and 5, shunted by boosting diodes 6 and 7 with feedback windings 8 and 9, a starting diode 10, shunted by the first capacitor 11, starting transistor. 12 and 'resistor 13; resistive divider 14, the second capacitor 15, two additional diodes 16 and 17 and 25 switching inductor 18.

The DC voltage Converter operates as follows.

When applying a constant voltage to the input of the device, the unlocking bias 30 enters through a resistor 13, an open transistor 12, a feedback winding 9, for example, a transformer 1, and through a parallel-connected limiting resistor 4 and a diode 6 to the base of the transistor 2. When the transistor 2 is opened, 35 to the corresponding A primary input voltage is applied to the primary winding of the transformer 1, and current flows through it. In the feedback winding 9 of the transformer 40 of the transformer 1, connected to the control circuit of the transistor 2, an ED C is induced to facilitate its further unlocking, and in the feedback winding 8 connected to the control circuit of the transistor 3, an EMF, which 45 locks it. In this case, through the switching inductor 18, the limiting resistor 4, the feedback winding 9 of the transformer 1 and the diode 7 starts to flow 50, coinciding in direction with the base current of the transistor 2. When the switching inductor 18 is saturated, the current through it increases sharply, which leads to decrease the base current of transistor 2 and 55 output it from saturation. Induced in all windings of the transformer 1 voltage is reduced to zero, and then reverse polarity. Now, the locking bias from the feedback winding 9 of the transformer 1 is supplied to the control circuit of transistor 2, and the unlocking to the control circuit of transistor 2. When switching transistors 2 and 3, the switching inductor 18 goes out of saturation and, trying to maintain its current unchanged, produces an EMF of the corresponding polarity, which is added up with a locking bias. The reverse blocking voltage applied to the base of transistor 2 can cause it to fail due to exceeding the permissible reverse voltage at the base-emitter junction. However, this does not happen due to the presence of additional diodes 16 and 17 and the second capacitor 15. After the converter enters the stable self-oscillation mode, the voltage on the capacitor 15 remains almost unchanged and close to the feedback winding voltage of the transformer 1. In this case, the transistor 12 is transferred using the resistive divider 14 to the closed state, disconnecting the start circuit. Subsequently, the energy of the reverse voltage surge at the switching inductor 18 is stored in the capacitor 15 and is used to maintain the transistor 12 in the closed state, due to which the energy of the primary source for controlling the start-up trip circuit is not used additionally, and the converter efficiency increases, the starting diode 10 and the first capacitor 11 are elements of the control circuit of transistors 2 and 3, allowing to reduce dynamic losses in transistors 2 and 3.

In the DC-DC converter, an increase in reliability is achieved by reducing the reverse voltage at the base-emitter junctions of the switching transistors 2 and 3 by connecting their bases through additional diodes 16 and 17 to the storage capacitor 15, as well as by supplying a start current symmetrically to the converter arms, providing the symmetry of its duty cycles and precluding the possibility of the transformer 1 entering one of the converter arms into saturation.

Claims (1)

Claim A DC voltage converter comprising a transformer whose secondary winding is connected to the output terminals, the middle terminal of the primary winding is connected to the first input terminal, and the extreme terminals are connected to the collectors of the switching transistors, the emitters of which are connected to the second input terminal, and the bases are connected through limiting resistors, shunted boost diodes 5, with the first outputs of the feedback windings, the second outputs of which are connected to the first output of the starting diode, shunted by capacitor, and to the emitter of the starting transistor, the collector 5 of which is connected to the first input terminal through the starting resistor, and the base is connected to the middle terminal of the resistive divider, the first terminal of which is connected to the first input terminal, the second capacitor connected by the first terminal to the second terminal of the starting diode and to the second input output, the switching cross-country switch connected between the bases of the switching transistors, characterized in that, in order to increase the efficiency and reliability by reducing the reverse voltage, the base is em switching transistors, two additional diodes are introduced, connected by the first terminals to the second terminal of the second capacitor, and by the second terminals to the corresponding bases of the switching transistors, while the first terminal of the second capacitor is connected to the second terminal of the resistive divider.