RU2028724C1 - Former of saw-tooth pulses of double frequency - Google Patents

Abstract

FIELD: pulse equipment. SUBSTANCE: former includes input and output wires 1 and 9, inverter 2, transistors 3 and 4, shunting resistors 5 and 6, time-setting capacitor 7 and load resistor 8. EFFECT: enhanced operational reliability. 2 dwg

Description

 The invention relates to a pulse technique and can be used as part of electronic automation devices, computer technology and power sources as a driver of a PWM signal.

 A device is known that contains five AND-NOT elements, a trigger, a timing RC circuit, and a variable resistor.

 This device contains a large number of elements and functional connections between them and does not allow receiving pulses of a sawtooth shape.

 A device is also known that contains an input inverter, two integrators, dividers of the comparison circuit, two AND-NOT elements and an AND-output element.

 This device also contains a large number of elements and functional connections between them.

 A device is also known that contains an input inverter, two diodes, a timing capacitor, and exclusive OR elements.

 In this device, the task of obtaining pulses of a double frequency of a sawtooth shape is not realized.

 The aim of the invention is to simplify the device and expand its functionality by obtaining pulses of a sawtooth shape, doubled frequency.

 To do this, two transistors of the same conductivity type are introduced into the double-frequency sawtooth pulse shaper containing an inverter, the input of which is connected to the input bus, the emitter of one of which is connected to the inverter output, the emitter of the other is connected to the inverter output and the input bus, the time-varying capacitor is turned on between transistor bases, the emitter-base transitions of which are shunted by resistors, the collectors are interconnected, with the output bus and through the load resistor with the housing bus.

 Figure 1 presents the circuit diagram of the device; figure 2 - timing diagrams of his work.

 The double-frequency sawtooth pulse generator comprises an input bus 1, an inverter 2, transistors 3 and 4, resistors 5 and 6, a capacitor 7 and a load resistor 8, an output bus 9.

 The pulse generator operates as follows.

On the input bus 1 is fed a pulse train with a duty cycle equal to or close to the meander. With the arrival of a positive edge at time t ₁ (U ₁ ) at the output of inverter 2, a low potential is established. The emitter junction of transistor 3 is shifted forward by the current flowing through the circuit: input bus 1, resistor 6, capacitor 7, emitter junction of transistor 3, output of inverter 2. Transitions of transistor 4 are biased in the opposite direction and it is closed: the emitter junction is biased by the voltage across the resistor 6, and the collector one - with the potential on the capacitor 7 with a minus applied to the base of the transistor 4. On the collectors of the transistors 3 and 4 - low potential, since the transistor 3 is open by the base current, the load resistor 8 also has a low potential. The capacitor 7 is recharged and at time t ₂ (U ₄ ) the voltage on it becomes equal to zero.

From the moment t ₂ (U ₄ ) on the basis of the transistor 4 and, accordingly, on the lining of the capacitor 7, a positive potential begins to grow, which grows on the section t ₂ -t ₃ (U ₄ ) as the capacitor 7 charges. Accordingly, the transistor 4 opens in the inverse version, and the collector junction of the transistor 3 is biased in the opposite direction. On the output bus 9, the potential increases linearly. On the plot t ₂ -t ₃ (U ₄ ) transistor 3 with a capacitor 7 operate according to the integrator circuit. Its collector load is a resistor 6 in conjunction with a transistor 4, which operates as an emitter charge follower of the capacitor 7, and the collector junction of the transistor 4 is biased in the forward direction. Thus, the transistor 4 on the plot t ₂ -t ₃ works as an emitter follower, using the base-collector junction for this. In this embodiment, the gain of the transistors is less than in normal operation, but high enough to work in this mode.

 On the collector of transistor 3, the potential grows linearly as the capacitor 7 charges due to negative feedback through it and through the collector junction of transistor 4, shifted in the forward direction.

At the moment t ₃ (U ₃ ), the potential at the input and output of the inverter 2 changes. Now the transistor 4 opens and the transitions of the transistor 3 are shifted in the opposite direction. The capacitor 7 is discharged and at the moment t ₄ (U ₃ ) its potential is reversed. Again, already on the t ₄ -t ₅ (U ₃ ) section, the potential on the output bus 9 is growing, and the transistor 4 together with the capacitor 7 work according to the integrator circuit with negative feedback from the collector to the base through the capacitance 7 and the collector junction of transistor 3. B in this case, the transistor 3 with the resistor 5 are the collector load of the transistor 4.

 Further, as the next pulses arrive at input 1 of the shaper, transistors 3 and 4 functionally interchange.

Moreover, on the output bus 9 there is a sequence of sawtooth pulses of doubled frequency (U ₉ ). On the bases of transistors 3 and 4, bipolar pulses are offset relative to each other by half a period. In areas of negative voltage t ₁ -t ₂ or t ₃ -t ₄ (U ₃ ; U ₄ ), capacitor 7 is discharged exponentially, and in areas of t ₂ -t ₃ and t ₄ -t _5, capacitor 7 is charged linearly for negative feedback account.

 By changing the value of the load resistor 8 can be achieved by adjusting the rate of change of a linearly increasing voltage of the output pulses on the bus 9, as well as their amplitude.

The proposed shaper can be used as a low-pass filter. With a decrease in the input pulse period is less
T _n ≅ R _5.6 ˙C ₇ ˙N,
where T _n is the period of the input pulses;
R _5,6 - resistors 5 or 6;
C ₇ - capacitor 7;
N is a certain coefficient.

The amplitude of the pulses decreases and at the output 9 there remains a potential close to zero. At the same time, with an increase in T _{n, the} amplitude of the output pulses is set at the same level.

Claims (1)

 DOUBLE-FREQUENCY Sawdog Pulse Shaper, comprising an inverter, the input of which is connected to the input bus, a capacitor and an output bus, characterized in that the first and second resistors, a load resistor and the first and second transistors, the emitters of which are connected respectively to the output and to the input, are introduced inverters, collectors - with an output bus and through a load resistor - with a common bus, a capacitor is connected between the bases of the first and second transistors, while the first and second resistors are connected between the base and the emitter the first and second transistors.

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