SU1501238A1 - Semibridge self-excited transistor converter - Google Patents

Abstract

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 goal is to increase efficiency and reliability by ensuring the switching of the power transistors at zero current. The converter consists of power transistors 1, 2, capacitors 7.8, switching 10 and output 3 transformers, the first winding 4 of which is connected to power transistors 1.2 and capacitors 7.8 through inductance 9 of the LC circuit. The RC circuit from resistor 15 and capacitor 16 forms a forward locking pulse for transistors 1.2 at the moment when the collector current drops to zero. 2 Il.

Description

to

SAE 00

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

The purpose of the invention is to increase efficiency and reliability by ensuring the switching of the power transistors at zero current.

FIG. 1,2-time diagrams, which explain the operation of the converter.

The converter contains power transistors 1, 2; output transfer mat 3 with singing 4, secondary 5 and additional 6 windings; capacitors 7, 8 and inductance 9 of a series resonant LC circuit; switch over transformer 10 with positive current feedback windings 11, voltage 12 and secondary windings 13, 14 connected to control inputs of power transistors 1 and 2; a resistor 15 and a capacitor 16 of a serial RC circuit; the capacitor 17 of the resonant LC circuit (capacitor 17 is shown on the circuit as a dotted line, since it can

absent and the role of inductance

9 can perform the leakage inductance of the output transformer 3 and the inductance of the switching transformer 10); load node 18 (in this case, a rectifier and filter), diodes 19-22, designed to reduce the absorption time (tpoc) of excess carriers in the region without power transistors 1, 2.

In practice, diodes can be included in the collector circuit of power transistors (shown in dotted lines in the diagram) to prevent current from flowing through the transistors in the opposite direction and unlocking the locked transistor after locking the other one.

The Converter operates as follows.

The starting of the circuit is carried out by one of the known methods of starting the autogenerators (the starting circuit is not given).

Suppose at time t,, transistor 1 opens. The current is closed along the circuit (Bx +) - 1 - 11 - 9 - 4 - B - (Bx-). The occurrence of current (i. Fig. 2) in the winding 11 of transformer 10 means a proportional change in the base current of transistor 1. The latter remains in the open state for a time equal to the half-period duration of the frequency of the resonant circuit (f), equal to

pej

 / 2Щ T.kS

where 0) 4, CY + Cj (in the absence of con5 0 5

0

50

five

Q

CK Densatopa 17;

 C, 7 (C-7 + Cg)

- in the presence of

with ;, + with + with

a capacitor 17; LK - total inductance

9SC - resonant circuit, reduced to the primary side,

The current in the primary circuit of the transformer 3, due to the presence of the resonant circuit, becomes zero at time t. This means reducing to zero and the base current of transistor 1.

The presence of diodes 19, 20 contributes to the rapid resorption of minority carriers in the base area and lock transistor 1. Interrupting the current in the circuit of transistor 1 leads to the appearance of reverse polarity voltage on the coil 6 of transformer 3 and, partially, on the windings of the transformer 10 This contributes to the appearance of a short current pulse through the RC-chain 15, 16 (t, 5, Fig.2) with the formation of the leading edge of the locking voltage at the base-to-junction transition (Vf in Fig. 2) of the transistor 1 and the unlocking voltage accordingly on the base-emitte transition p of transistor 2. A forced process of locking transistor 1 and unlocking of transistor 2 occurs. Current 14 (Fig. 2) in the primary circuit in the second half-period also begins to increase from zero, but in the opposite direction, repeating the shape and magnitude of the current

the first half period to time tj, I

whereupon the processes described are repeated continuously and periodically. In this case, the switching of transistors always takes place at a zero value of the current through them, depending on the type and nature of the load on the converter. The current i | j in shape can be either close to the sius (1ide with active or capacitive load (for example, when the filter is miter, starting with capacitance 17, as

rolled in FIG. 1 and 2 dotted line), or may be in the form of a truncated (at the level of the load current) sinusoid - with the inductance of the response of the output filter or load (the capacitor 17 is absent).

Claims (1)

Invention Formula Half-bridge transistor converter with self-excitation, containing power transistors, output transformer with primary, secondary and additional windings, series resonant LC circuit, connected to the primary circuit 12386 output transformer, and a switching transformer with positive current and voltage feedback windings and secondary windings connected to the control inputs of the power transistors, characterized in that, in order to improve efficiency and reliability 10 by ensuring the switching of the power transistors at zero current, a KS-chain is introduced into it, through which the voltage feedback winding ) 5 switching transformer associated with the additional winding of the output transformer. ;five Compiled by V.Handogin Editor M.Tovtin Tehred M.Hodanich Proofreader I.Musk Order 4887/54 Circulation 646 VNISHI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 1) 3035, Moscow, Zh-35, 4/5 Raushsk nab. Y Phie, 2 Subscription