SU550758A1 - Control unit for half-bridge amplifier - Google Patents

Description

one

The invention relates to the field of converter technology and can be used in power supply and electric drive systems for converting direct current into alternating current.

In known converters containing a bridge or half bridge of power transistors, for protection against "through currents in the switching process of power transistors, the transistor control device is made semi-dependent, i.e. half of the transistors of the power bridge is controlled from removed from the additional windings of the output transformer. In these circuits, the structure of the output transformer is complicated.

The half-bridge of the transistors of the pre-terminal amplifier is inserted into the semi-dependent excitation circuit, the output terminal of which is connected to the output terminal of the half-bridge via a control transformer, the secondary windings and the latter are connected to the input of the power transistors.

The disadvantage of this circuit is the need to use pre-finite transistors designed for the same voltage as the power ones.

The purpose of the invention is to increase the reliability and reduce the cost of the device by making a pre-terminal amplifier in the form of a bridge of low-voltage (more expensive) transistors powered from a separate source, the two of which are controlled by an external signal, and the other two are from the secondary transformer, primary the winding of which is connected between the output terminals of the power and the additional half bridge of the transistors.

The drawing shows a diagram of the device.

The power amplifier U contains a bridge of power transistors TI and T2, controlled via a Tpi transformer from the bridge transistors Gz-1b of the pre-end amplifier U2, which

it is powered by a separate low voltage source of constant voltage.

A half-bridge of additional transistors T, Tz is connected to the main power source, between the output terminal of which and the output terminal of the power half-bridge Tj T2 the primary winding of the additional transformer Tra is connected.

The secondary windings "i and 0) 2 of this transformer are connected to the input of transistors

T and TS, and cos and (l - with the input of transistors

Tz and T4. TS and Te transistors are controlled

external signal from master oscillator

SG through the transformer Trz.

The proposed scheme works as follows.

in a way.

Suppose that the transistors T2, Tz, Tb, Tu were open (the signals on the secondary windings have a polarity of “+ on the point). At a certain point in time, the polarity of the signal of the master oscillator generator ZG is changed, and the transistor T5 is unlocked and the Te transistor is locked, the voltage across the windings of Tpi decreases to zero, and transistor T2 begins to lock. While the process of resorption of excess carriers in the base of the transistor TZ is in progress, the voltage drop between its electrodes is close to zero, the transformer Tr2 and the transistors Tm, TS, T3, T4 are in the same state. This ensures the absence of voltage across the windings of Tr and the transistor Tj does not open.

Only after the termination of the indicated process of resorption of carriers is complete, the transistor TZ is completely closed, the voltage on the windings Tp2 disappears and the transistors switch, and then Ta-T4. The voltage across the windings Tpi changes polarity and the transistor Ti is turned on. In this way, the simultaneous open state of the power transistors and the associated through currents are eliminated, i.e., the reliability is improved.

In this case, the proposed amplifier can

use cheap low-voltage Tz-tb transistors. And additional transistors Tu, TS have a small value of the working current of the collector, and therefore their cost is also small.

Claims (1)

Invention Formula A half-bridge power amplifier control device comprising a pre-terminal amplifier with a master oscillator and a control transformer, the secondary windings of which are connected to the input of the power transistors, characterized in that In order to increase reliability, the pre-end amplifier is designed as a bridge of control transistors connected to the terminals for an additional power source, and for the main power source the half bridge of the additional transistors is connected, the output terminal of which is connected to the output terminal of the power amplifier through the primary winding of the additional transformer, the secondary windings of which are connected to the inputs of additional transistors and two control transistors, and the inputs of two other control transistors are connected to said driving oscillator. about