CS252208B1 - Power Driver Connection - Google Patents

Abstract

The switch is connected to a voltage of one polarity and a voltage of the other polarity to the emitter of at least one power transistor, the switch being formed by at least one complementary pair of transistors, the bases and emitters of which are connected to each other. The power driver is connected in a transistor welding power source.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a power driver circuit, in particular for driving power transistors, consisting of a driver connected via a switch and a forming circuit to a power transistor.

The transistor power driver circuits used hitherto typically utilize the reverse polarity reversal occurring on the drive transformer at the termination of the drive pulse to accelerate the trip of the power transistor. In other cases, complex circuitry is used, for example, for charging and discharging capacitors intended for this purpose. With such wiring, it is difficult to provide the desired excitation waveform for larger variations in its length, as is needed, for example, in applications with transistor converters at non-constant load.

In applications with a constant excitation pulse length, higher transistor losses occur with conventional excitation circuits. At the same time, the magnitude of the voltage applied to the base-emitter of the power transistor in the reverse direction cannot be precisely defined in the applications used so far, resulting in the risk of undue stress on the power transistor.

In addition, for excitation of transistors of particularly high power (current above 30 A and voltage above 500 V), there is a problem of ensuring a sufficient steepness of the excitation pulse front, the excitation transformer is of considerable size and at the same time disproportionately large losses in excitation circuits.

The power exciter of the invention can be substantially reduced or eliminated. Its principle is that the switch is connected to a voltage of one polarity and second to a voltage of the other polarity with respect to the emitter of at least one power transistor. The switch comprises at least one complementary pair of transistors whose bases and emitters are connected to each other.

The circuitry according to the invention provides optimum pulses for power transistors from a minimum required length to an arbitrarily large pulse length. If long pulses are required galvanically separated, the flip-flop follows the isolation transformer or the isolation is made by an optoelectronic coupling.

By providing a good excitation pulse, the switching and trip losses of the power transistors can be minimized, and since the transistor is virtually saturated, the on-state losses are also minimized.

Even when the transformer is used as an exciter isolation element, the wiring pulse width can be varied over a wide range without the risk of deteriorating its quality. The shape and magnitude of the excitation current can be adjusted by using shaping members connected as needed in the excitation circuit.

The most common effort is to increase the steepness and amplitude of the excitation impulsus at its beginning.

A specific example of wiring is shown in Fig. 1, where the driver 2 is connected to a power transistor 4 via a switch 2 and a shaping circuit 2. -) with respect to the emitter of the power transistor T4, the switch 2 being formed by a complementary pair of transistors T2, T3, whose bases and emitters are connected to each other. A trigger pulse is supplied to the first winding of the pulse isolation transformer TR. The first transistor T1 of the exciter 2 is switched from the second winding TR with the transformed trigger pulse. Consequently, hitherto closed transistor T3 complementary pair off (through a resistor R was still the base of transistor T3 complementary pair connected to the negative pole, the first transistor Tl has been opened) and far off transistor T2 complementary pair closes and applies a positive voltage through a shaping circuit 2 based ^on of the power transistor T4, which is thereby switched.

and

By using a complementary pair of transistors T2, T3, fast switching on and off is ensured, and there can be no state in which both transistors are practically switched on and connect both poles of the source into a short circuit. The shaping circuit 2 provides, by means of capacitor C, an increase in the slope and amplitude of the excitation current when switching the power transistor T4. At the end of the excitation impulse, the first transistor T1 switches off. This changes the voltage of the complementary pair of transistors T2, T3 (negative voltage is applied to the base R) from positive to negative, and thus transistor T2 starts to trip, transistor T3 closes and connects negative voltage based on power transistor T4, thereby accelerating turning it off.

In other possible connection methods according to the invention, in the connected bases and / or emitters and / or collector circuits, complementary pairs of transistors T2, Z2 are connected by resistors, capacitors or inductances or series and / or parallel combinations of their connections.

The connection of the power driver according to the invention is realized, for example, in a transistor scaling source.

Claims (2)

Wiring of a power driver, in particular for driving power transistors, consisting of a driver connected via a switch and a shaping circuit to a power transistor, characterized in that the switch (2) is connected to both polarity (A) and second polarity (B) with respect to the emitter of at least one power transistor (T4), the switch (2) being formed by at least one complementary pair of transistors (T2, T3) whose base and emitters are connected to each other. Power driver circuit according to claim 1, characterized in that in the connected bases and / or emitters and / or collector circuits a complementary pair of transistors (T2, T3) are connected resistors, capacitors event. inductance or a series and / or parallel combination thereof.