SU588618A1 - Controllable pulse generator - Google Patents

Description

(54) ADJUSTABLE PULSES GENERATOR

the diode 7, the limiting resistor 5 and the part of the resistor 2 that is connected between its engine and the output of the resistor 5. The voltage at the second (according to Fig. i - right) output of the trigger is close to zero, since the voltage on the emitter of the single-junction transistor is not may be less than the residual voltage Uost component of +2, + 3 V, then the diode 8 is locked, it breaks the circuit consisting of a resistor b and the right side of the variable resistor 2, this circuit does not affect under this trigger condition to work the device.

As the capacitor charges from the output voltage of the trigger through the resistor 5 and the left side of the resistor 2, the voltage across the capacitor 1 increases and reaches the turn-on voltage of the single junction transistor 3. The turn-on voltage is determined by the equality, where E is the supply voltage, c is unijunction transistor parameter. Next, the single junction transistor turns on, capacitor 1 is discharged through the emitter circuit of the single junction transistor 3, creating a positive output pulse on the load resistor 4 in the first base circuit of the single junction transistor 3. This positive pulse arrives at the counting input of the trigger 9 and switches the specified trigger. The voltages at the outputs of the trigger 9 are reversed. A high positive level of the output signal is located at the second (in Fig. 1, right) output of the trigger 9. Diode 8 opens, diode 7 closes, the voltage across the capacitor, which during the formation of the output pulse of the cascade at the single junction transistor decreases to t / off is now starting to increase, since capacitor 1 is charged through diode 8, resistor 6 and the right side of resistor 2. A circuit with resistor 5 is broken and turned off by diode 7 and does not affect the operation of the device.

At the moment when the voltage on the capacitor 1 rises to the value bvkl, the trigger switches again and the time specifying the resistance of the device changes. The alternator charge resistance at a single junction transistor cannot be less than the minimum allowable value determined by the switching current of the single junction transistor. Resistors 5 and 6 are designed so that when adjusting the time, the impedance is not less than the permissible value.,

The coefficient T K can be adjusted from zero to one when adjusted, then during the first part of the period the capacitor is charged with a constant time

C, (, + CL),

where Ci is the capacitance of the capacitor 1; 5 - resistance of the resistor 5; K. - coefficient of inclusion of variable

resistor 2;

57 - resistance of variable resistor 2; The duration of this interval

. C, {R, + KR) ln, °.

iJl - bvcl

Where

In Q const. / - ГУвкл

15 Accordingly, the second part of the period matters

. CJ, + (l- / C).

KR - left resistance value

where parts of resistor 2, from the slider to the output connected to resistor 5;

(1-K) R is the resistance value of the right part of the resistor 2, from the slider to the output connected to the resistor 6;

JRs is the resistance of the resistor 6. The period T is determined by the equality

-. + V

Substituting the found values of TI and tg, we see that the period T when adjusting does not depend on the switching coefficient K a depends only on the total value R, which

when adjusting does not change, i.e.

Г: СЛ /, + / С / + / .- f (а-С, К, + 1, + Щ

Consequently, the circuit ensures a constant oscillation period with a wide range of adjustment of the duty cycle.

Claims (1)

1. Olsevich, A.E. Two-base diodes in automatics, M., Energie, 1972, p. 37.