SU599319A1 - Device for control of power transistor of a converter - Google Patents

Description

one

The invention relates to the field of electrical engineering and can be used in converters and key power amplifiers for controlling power trans. switching-mode sistors.

Power transistor control devices are known that contain a switching transformer, the secondary winding of which is connected to the input circuit of the power transistor through a rectifier and a base resistor.

After locking the power transistor in such a circuit, the base circuit is open-circuited, which causes additional losses in the transistor.

Also known are circuits with an onboard switching transformer, the secondary winding of which is connected to the input of the power transistor through the base resistor of this circuit when the core of the transformer is saturated, the transistor turns off and the locking conditions are improved relative to the previously specified circuit. However, the resorption time of excess

carriers in the base of the power transistor remains quite large, since the locking occurs passively.

The purpose of the invention is to increase the efficiency of the converter by reducing the duration of the process of turning off the power transistor.

This is achieved by the fact that in the proposed device, parallel to the power input

the transistor controlled from the switching transformer through the base resistor, includes an additional transistor of the opposite conductivity type, the emitter of which is connected to the base of the power

transistor, and the collector - with the emitter of the power transistor. The base of the additional transistor is connected via an additional resistor to the second output of the secondary winding of the switching transformer.

The drawing shows a diagram of the proposed device on the example of a push-pull half-bridge self-exciting transducer.

Claims (2)

The converter contains a switching transformer 1, the emitters directly to the secondary windings, and the power transistors 4 and 5 of the converter are connected to the bases through the base resistors 2 and 3. A power transformer 6 is installed at the output of the converter, the output rectifier 7 is connected to the secondary winding. Additional transistors 8 and 9 of opposite conductivity connected to the emitter and collector are connected to the secondary winding of each transistor of the converter, respectively 11 with a common point corresponding to the winding of the coil of the transformer and the base resistors 2 and 3, the process of turning off each of the transistors 4 and 5 begins when the core of the switching transformer becomes saturated The voltage across the windings of the switching transformer becomes almost zero, In a saturated transistor, the process starts, the discharge of the excess charge in the base. During the discharge process, the voltage at the base of the transistor changes little, up to the moment of its discharge from saturation, when it, just like on the winding of the commutating transformer, is changed in the absence of additional transistors 8 and 9 discharge occurs through the resistance of the base transformer. resistor and corresponding winding. These resistances limit the discharge current and increase the resorption time. The difference in the time of dissipation into adjacent half-periods and the asymmetry of these half-periods turn out to be significant. An additional transistor connected to the main transistor of the converter decreases at the voltage of the switching transformer winding. An additional circuit is formed to discharge the excess charge in the base of the saturated transistor of the converter. The resistance of the applied additional transistor is many times less than the resistance of the base resistor. Therefore, the discharge current is increased, and the resorption time of excess carriers is reduced. The difference in dissolving time into adjacent halfperiots, and consequently, the asymmetry of the half-periods is reduced. Due to this, the one-sided bias of the transformer 6 is eliminated and the efficiency of the converter increases. The invention The control device of the power transistor of the converter, comprising a switching transformer, the first output of the secondary winding of which is connected to the emitter of the power transistor, and the second output through the base resistor is connected to the base of the power transistor, so that In order to increase the efficiency of the converter, by reducing the duration of the transient switching off of the power transistor, an additional transistor of the opposite conductivity type is introduced, the emitter of which is connected to DNAase power transistor, the collector to the emitter of soy Diven power transistor, and whose base is connected via a further resistor to a second terminal of the secondary winding of the switching transformer. Sources of information taken into account in the examination; 1. Certificate of author No. 275126, cl. And 03 to 17/56, 1969. 2.Patent QUA No. 2774878, cl. 331-113, 1956. -CZZh-r r .7 .