SU517987A1 - Key power amplifier - Google Patents

Description

(54) KEY POWER AMPLIFIER

one

This invention relates to electrical engineering and can be used in power converters.

Known key power amplifier with a matching transformer at the input, containing at least one pair of power transistors, each of which is connected to an auxiliary transistor according to the scheme of a composite transistor using a current transformer, the primary winding of which is connected in series with the load, and the secondary connected between the bases and the emitters of the respective power and auxiliary transistors.

However, a known key amplifier has low efficiency and power gain.

The purpose of the invention is to increase the efficiency and power gain by reducing dynamic and static losses. For this, at least one pair of secondary windings of a matching transformer is connected to each composite transistor, one of them is connected through a resistor between the bases of the power and auxiliary transistors, and the second is connected to the base of the power transistor, the emitter of which is connected through the oppositely connected , with respect to the control transition of this transistor, the diode to another output of the secondary winding.

The drawing shows the electrical circuit of the proposed amplifier.

The key power amplifier contains composite transistors 1 and 2, 3 and 4, 5 and 6, 7 and

8, each of which is respectively a power 2, 4, 6 or 8 and auxiliary 1, 3, 5 or 7 transistors connected by current transformers

9,10, the primary winding of which is connected in series with the load 11; transformer secondary windings are connected between

bases and emitters of the corresponding power and auxiliary transistors. The control unit 12 is connected to the primary winding of the matching transformer 13, at least one pair of secondary windings

which is connected to each composite transistor 1 and 2, 3 and 4, 5 and 6, 7 and 8, and one of them is connected through resistor 14 between the power bases 2, 4, 6, 8 and the auxiliary 1. 3, 5, 7 transistors and the second is

one output is connected to the base of the power transistor 2, 4, 6, 8, the emitter of which is connected through a counter diode 15 connected to the control transition of this transistor to another output of the secondary winding. Diodes 16 serve to reduce power consumed from control circuits. And resistors in the control circuits serve to limit the base currents.

Key power amplifier works as follows.

If the composite transistors 1, 2 and 7, 8 are open, and the transistors 3, 4 and 5, 6 are closed, then the polarities of the voltages on the circuit elements are indicated in the drawing. In this case, the auxiliary transistor, for example, 1, is open by the sum of voltages on the secondary winding of the transformer 9 and on the upper secondary winding of the matching transformer 13. The voltage on the secondary winding of the transformer 9 is almost equal to the input voltage of the power transistor 2. Transistor 2 is open by the collector current of the auxiliary transistor 1 and is in saturation mode. The auxiliary transistor, for example 3, is closed by the sum of the voltages on the secondary winding of the transformer 9 and on the upper secondary winding of the matching transformer 13. The power transistor 4 is locked by the voltage on the lower secondary winding of the matching transformer 13.

The indicated state of the circuit is maintained until the polarity of the control voltage is changed. In this case, the switching off of the composite transistor 1, 2 occurs with some delay, due to the resorption of minority carriers in the bases of these transistors. However, during the specified time interval, the inclusion of the composite transistor 3, 4 cannot occur, since the voltage on the windings of the current transformer 9 does not change the sign and, therefore, negative feedback acts in the control circuit of transistor 3. The change in polarity of the voltage on the windings of the current transformer 9, and consequently, the inclusion of the composite transistor 3,

4, a lisch may occur after the power transistor 2 leaves the saturation mode, which prevents short-circuit currents from flowing through the transistor. After the polarity of the control signal is changed, the circuit goes into another quasi-stable state, in which the composite transistors 3, 4 and 5, 6 are open, and the transistors 1, 2 and 7, 8 are closed. Thereafter, the processes in the circuit are repeated.

At the same time, the magnitude of the control voltage must be sufficiently low to turn on the auxiliary transistors 1.4, 5, 7 with a minimum collector current.

Claims (1)

Invention Formula A key power amplifier with a matching transformer at the input, containing at least one pair of power transistors, each of which is connected to an auxiliary transistor according to the scheme of a composite transistor using a current transformer, the primary winding of which is connected in series with the load, and the secondary ones are connected between the bases and the emitters of the respective power and auxiliary transistors, characterized in that, in order to increase the efficiency and gain in power by reducing the dynamic Sgiach and static losses, each composite transistor is connected to at least one pair of secondary windings of the matching transformer, one of them via a resistor connected between the bases power and auxiliary transistors, and the second - one output connected to the base of the power transistor, the emitter of which is connected through a counter-connected, in relation to the control transition of this transistor, the diode to another output of the secondary winding.