SU428531A1 - PULSE GENERATOR - Google Patents

Description

one

The generator can be used, for example, as a master oscillator and phase-shifting element in thyristor converter control systems when designing time sensors and various voltage-frequency converters.

Known pulse generator containing the equivalent of a two-base diode, vnolnepny on two transistors of different conductivity type, the emitter of the first of which is connected to the middle output of the serial / C-chain, and the second emitter through the current limiting resistor to the second capacitor of the C-chain and to the output of the divider resistors, with a different output of the voltage divider connected to the common output of the power source, and a pulse transformer. The switching conditions of the equivalent of a two-base diode of such a generator depend on the parameters of the component transistors and the charge current of the capacitor / C-circuit, as a result of which the generator is not reliable enough and is stable in operation.

The aim of the invention is to increase the stability of the pulse generator. This is achieved by the fact that between the power supply and the common connection point of the current-limiting resistor, the capacitor ./ of the C-circuit, and the voltage divider are included

an additionally inserted diode, and the common connection point of the base of the first transistor and the collector of the second transistor is connected via the secondary winding of the transformer with an average output of the voltage divider.

The drawing shows a schematic diagram of the proposed generator

The generator contains the equivalent of a two-base diode, made on transistors / 0 and 2 of different tin conductance; Serial QC chain consisting of resistor

3 and capacitor 4; a voltage divider on resistors 5 and 6, a current-limiting resistor 7, a power supply 8, a diode 9, a pulse transformer 10, and a diode 11 that shunts the primary winding of the transformer. Instead of diode 9, a control junction of transistor 12 can be used. The emitter of transistor 1 is connected to the middle terminal of the C-chain, the second terminal of resistor 3 of which is connected to the main terminal of the power supply.

The emitter of transistor 2 through a resistor 7 is connected to the second capacitor plate

4 and to one pin of a voltage divider, the other pin of which is associated with the common pin of the power source. The common junction point of the collector of the transistor Y and the base of the transistor 2 is connected through the primary winding

a transformer with a power source, and the common connection point of the transistor base / and the collector of transistor 2 is connected via the secondary side of the transformer to the middle terminal of the voltage divider. A diode 9 is connected between the power supply and the common connection point of resistor 7, capacitor 4 and voltage divider.

The generator works as follows.

At the first moment after switching on the voltage of the power supply source 8, the voltage on the capacitor 4 is zero, the transistors are in the cut-off state: the zmitter junction of transistor 1 is locked by the voltage difference across the resistor 5 and the capacitor 4, the emitter junction of transistor 2 is voltage on a diode 9 through which a voltage divider current flows and a charge current of a capacitor 4 flows.

As the voltage across the capacitor increases, the reverse voltage at the emitter junction of the transistor / decreases and after changing the sign of this voltage, the transistor 1 changes from a cut-off state to the active state, due to the positive feedback in the generator, the process of "key transistors. The initial stage of this process proceeds without the fate of transistor 2 due to the action of positive feedback through the transformer 10, as in a blocking generator. With the output of T1p.nz1stor 2, a positive feedback of the equivalent of a two-base diode comes into effect in the active region, as a result of which the transistors become saturated, and the capacitor begins to discharge. With a sufficiently small magnetizing inductance of the transformer during the discharge of the capacitor, a reverse voltage is applied to the diode 9, and if the ratio of the number of turns of the transformer secondary winding to the number of turns of the primary winding exceeds a certain minimum value determined by the ratio of the resistances of the resistors 5, 5 and 6, the diode 9 is locked immediately after the transistors are turned on.

Thus, during the discharge of the capacitor, the emitter of the transistor 2 and the driver are disconnected from the connector, the driver is disconnected from the source and the current flow in the emitter circuit of this transistor is possible only with the presence of the discharge current of the capacitor. This is the advantage of a pulse generator.

The magnetizing inductance of a transformer is chosen such that the rate of voltage reduction on its windings is substantially higher than the discharge rate of capacitor 4. At the same time, the discharge of the capacitor, the pulse repetition rate and frequency are practically independent of the parameters of the transformer itself. , switching process.

During the formation of a pulse in the transformer windings, currents are set that tend to turn off the equivalent of a two-base diode, and when the discharge current of the capacitor approaches the value of the current flowing through the resistance of the resistor 6, the transistors / and 2 close, even if the current gain of each of them equals 1. Energy stored

in the magnetization circuit of the transformer, contributes to the effective resorption of the main charge carriers from the base areas of the transistors; an excess of this energy is dissipated in the shunt diode.

After the transistors are turned off, the described processes are repeated with the difference that the capacitor is charged from a certain initial level of voltage equal to the voltage on it at the moment of switching off the transistor.

The pulse generator works steadily in the absence of the secondary winding of the transformer. However, the minimum permissible charge current of a capacitor in the C-chain at

this increases, the frequency range of generation is reduced. Despite this drawback, this option is of great practical importance, since it allows the use of switching devices with one

control electrode.

The load of the generator, of course, affects its operation. In this generator, it is possible to obtain rectangular pulses with a very small influence of the load,

if, as a nonlinear element (diode 9), use the control transition of the output key, for example, the emitter transition of the transistor 12.

Subject invention

A pulse generator containing the equivalent of a two-base dyad, performed on

two transistors of different conductivity type, the emitter of the first of which is connected to the middle output of the series / C-chain, the second output of which is connected to the common output of the power source,

the emitter of the second transistor is connected through a current limiting resistor to the second capacitor / C-capacitor plate and to one output of a voltage divider on the resistors, the other output of which is connected to the common

the output of the power source, and the common collector connection point of the first transistor and the base of the second transistor is connected through the primary winding of the transformer, bounded by a diode, to a power source,

characterized in that, in order to increase stability, between the power supply and the common connection point of the current-limiting resistor, the C-chain capacitor and the voltage divider are additionally included

the diode entered, and the common connection point

The bases of the first transistor and the collector of the second are connected via the secondary winding of the transformer with an average output of the voltage divider.