SU762144A1 - Pulse train shaper - Google Patents

Description

one

The proposed device relates to a pulse technique, can be used in thyristor startup devices and tunable pulse generators.

A device for forming a sequence of pulses of variable duration, containing the reference pulse generator, the element And, the control trigger, the trigger-shaper [1].

However, the design of this device is complex and has limited functional characteristics.

A known generator of a series of pulses, containing a generator of pulses on a unijunction transistor, an additional transistor (2].

Known generator has insufficient functionality.

The purpose of the invention is to expand the functionality of the scheme.

To achieve this goal, a pulse series generator containing a pulse generator on a single junction transistor, parallel to the timing capacitor of which a transistor is connected, the control electrode of which is connected to two resistors, the second output of one of which is connected to the power supply bus, a zener diode, a capacitor, a transistor and a resistor are inserted 2 enabled

between the base and the emitter of the inserted transistor, the collector of which is connected to a resistor, the other output of which is connected via a capacitor to a common bus,

5 which is connected to the emitter of the inserted transistor, the base of which is connected via a zener diode to the generator output.

FIG. 1 shows the principal

Ιθ is the electrical circuit of the proposed pulse generator; in FIG. 2 - time dependences of the voltages at the output of the device and at the capacitor of the timing circuit.

15 A resistor 2 is connected to the emitter – base of transistor 1. Transistor 1 with a resistor 3 in the collector circuit is connected in parallel to a capacitor 4 of the timed circuit including resistor 5. Parallel to the capacitor 4 is connected a gate – drain of the field-effect transistor 6. Between the source of transistor 6 and the positive one the resistor 7 is connected to the power bus. In parallel to the source-to-junction transistor 6

25, a capacitor 8 is connected. The emitter of the unijunction transistor 9 is connected to the source of transistor 6. Resistors 10 and 11 are connected to the base circuit of transistor 9. A Zener diode 12 is connected between the output of the device and the base of transistor 1.

762144

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When you turn on the supply voltage, the capacitor 4 is charged through a resistor

5. The increasing positive voltage on the capacitor 4 leads to the locking of the field-effect transistor 6 and an increase in the voltage at its source. When the voltage at the source of the transistor 6 reaches the turn-on voltage of the transistor 9, the cascade on the transistor 9 begins to generate unipolar positive filling pulses of a rectangular shape. The pulse repetition frequency is regulated by a resistor 7. Each positive pulse through Zener diode 12 triggers transistor 1, and for the duration of this pulse, capacitor 4 is discharged through resistor 3 and transistor 1.

The time constant of the discharge of the capacitor 4 is much longer than the pulse width of the generator and can be adjusted by the resistor 3. Due to the discharge of the capacitor 4, the positive voltage at the gate of the transistor 6 decreases, which leads to its unlocking. A decrease in the source-drain resistance of the opening transistor 6 causes a decrease in the equivalent resistance of the charge circuit of the capacitor 8, which leads to an increase in the frequency of the pulses at the end of the series. When the voltage at the source of the transistor 6 falls below the turn-on threshold of the transistor 9, the generation of pulses stops. The capacitor 4 is charged again until the switching on of the transistor 9, and the process of forming the next series of pulses repeats. The duration of a series of pulses is regulated by a resistor 3, the frequency of filling the pulses by a resistor 7, and the repetition period of the series by a resistor 5.

Unlike the prototype, the scheme of the proposed device contains only three active elements. In addition, the output pulses of the series are modulated in frequency so that at the end of the series

four

pulse frequency increases. The shape of the output pulses is shown in FIG. 2a The use of such series is advisable in thyristor startup circuits, as it allows to improve the start of the thyristor while reducing the supply voltage to a minimum. In the process of generation on the capacitor 4, a voltage pulse Y! step form, an idealized graph of which is shown in FIG. 2. Thus, in the scheme of the proposed device, it is possible to simultaneously receive voltage pulses of a stepped shape and a series of rectangular pulses modulated in frequency, which allows the functional characteristics of the device to be expanded.

Claims (1)

Claim A series of pulses generator containing a pulse generator on a unijunction transistor, parallel to the timing capacitor of which a transistor is connected, the control electrode of which is connected to two resistors, the second output of one of which is connected to the power supply bus, in which Zener diodes, a capacitor, a transistor and a resistor connected between the base and the emitter of the inserted transistor, the collector of which is connected to the resistor, and another terminal which through a capacitor is connected to a common bus, which is connected to the emitter of the input transistor, the base of which is connected via a zener diode to the generator output.