FR2471082A1 - SWITCHABLE GENERATOR DELIVERING FROM - Google Patents

Abstract

SWITCHABLE GENERATOR DELIVERING PULSES IN THE SHAPE OF A SAW TOOTH AND IN THE SHAPE OF A TRIANGLE AND INCLUDING A CONSTANT CURRENT SOURCE 1 TO WHICH IS CONNECTED A CAPACITOR 2 AS WELL AS A DISCHARGE TRANSISTOR 3 WHICH IS CONNECTED IN PARALLEL TO THIS CAPACITOR 2.

Description

The present invention relates to a switchable generator delivering

  sawtooth and triangle shaped pulses comprising a constant current source to which a capacitor is connected as well as a discharge transistor which is connected in parallel to this capacitor. The invention relates to the technique of measurements and

  communications where we create, by simple means,

pulses with variable parameters having a tooth shape

  saw and a triangle shape.

  Already known generators of simple design which deliver pulses in the shape of a sawtooth

  (Rfe 1977 H 19/20 page 671) and in which condensates

  torers are charged through a source of

  constant rant. The drawback of these simple generators known to date lies firstly in the fact that the characteristic values of the pulses, insofar as they can be controlled from the outside, influence each other

mutually when varying parameters and second-

This is due to the fact that the output voltage is, at rest, highly dependent on the components and their drift. In the mentioned process, the speed of rise and at the same time the amplitude of the sawtooth pulse vary with the control. Rise speed and amplitude can be adjusted by applying voltages

  from an external source.

  In order to remedy the mutual influence mentioned previously, it is also known to make the various characteristic values of the pulses stable (Stabilization of the amplitude for example in Rfe 1975/6 page 195). However, this stabilization does not allow a

  simple variation. In the embodiment described in the publication

  cation mentioned, it is also not possible to adjust the speed of the rise or increase and the amplitude at

using DC voltage from an external source.

  In addition, the output voltage is not exactly defined in the quiescent state because it is influenced by the

  characteristics of a transistor present in the circuit.

  Generators delivering sawtooth pulses cannot be switched to provide triangular pulses. However, certain generators are known which are made to supply pulses of different shapes in order to allow use

  universal (for example functional generators of

for controls and measurements), however these genera

  rators are complicated and require a number of components

important health which considerably increases their cost price. To overcome this drawback, it has been necessary, to date, to be content with solutions constituting a compromise between universal use, in particular as regards their ease of use, and the

precision of the pulses produced.

  The object of the present invention is to increase the precision and the ease of use as well as the

  reduction of the cost price while allowing use

  universal station and generator control by calibration

  culatrice. The object of the invention is also to create a

generator which delivers, as desired, triangular pulses

  slender or sawtooth-shaped with tension

very precise tie in the resting state and allowing free choice of the position of the sawtooth relative to the zero line and in which the amplitude, the resting time and the speed of rise of the pulses can be adjusted separately and without interaction, - especially by a command by calculator, and which provides a rectangular impulse

  which is synchronous to the sawtooth.

The above problems are solved in accordance with the invention by a generator which is characterized in that the output of the constant current source is connected, on the one hand, with each of the inputs of two comparators and, on the other hand, via a limiting amplifier, with the first input of a decoupling amplifier, the second input of which receives a variable control voltage (Uv) as offset voltage, in that the output of the first comparator, of which the second input is connected to a reference voltage (U ref), is connected

optionally thanks to a switch, either at the entrance of a low-

  monostable route, ie at the first entrance to a storey

  phase version, in that the output of the second comparison

  tor, whose second input is at zero potential, is connected to the first input of a NAND element with NAND function, to decouple a synchronous rectangular pulse, and to the second input of the phase inversion stage, whose

  the third input receives a charging voltage for the con-

  densifier and the output of which is connected to the input of the source

  constant current, and in that the output of the rocker mo-

  nostable is connected, on the one hand, to the second entry of the

element NAND and, on the other hand, via a door, which can be blocked, at the control input of the discharge transistor which is polarized in opposition to the charge voltage

of the capacitor.

It is advantageous to control the charging voltage,

  the switching voltage of the lockable door, the voltage

  offset offset and reference voltage using a

electronic calculator.

  The minimum and maximum values of the capacitor voltage and therefore the rise slope of the sawtooth are determined by two comparators which deliver the pulses to create the sawtooth shape or the shape

  triangular as well as the rectangular function syn-

sawtoothed. The polarization voltage of the tran-

discharge sistor is precisely limited during rest time. The characteristic values of the pulses can

  be adjusted separately due to a variation in the voltage

  external sion, which offers the possibility of control by electronic calculator. This generator makes it possible to create variable pulses in the shape of a sawtooth and a triangle as well as pulses of rectangular shape and synchronous to the pulses of a sawtooth despite the use of a small

number of components.

Various other features of the invention

  moreover emerge from the detailed description which follows.

  An embodiment of the object of the invention is shown, by way of nonlimiting example, in the accompanying drawing. The single figure represents the block diagram of the

generator according to the invention.

  The output of a constant current source 1 is connected to a capacitor 2 at ground potential, to the collector

of a discharge transistor 3, at one of the inputs of two com-

  parateurs 4, 5 and, via a li-

  miter 6, at the non-inverting input of a signal amplifier

coupling 7. The output A1 of the decoupling amplifier 7 is coupled in feedback by a resistor 8 at the input

non-inverting which is connected to an offset voltage va-

  reliable Uv via a resistor 9. The output of comparator 4, the second input of which is at ground potential, is connected both to the first input of a phase inversion stage 10 and to the first input of a NAND element 11 with NAND function for decoupling a pulse

rectangular synchronous via output A2. Coming out of the compa-

  generator 5, the second input of which receives a reference voltage

  rence Uréf, is selectively connected via a switch 12, or to the input of a monostable rocker 13,

  either at the second input of the phase inversion stage 10.

A charging voltage UL is applied to the third input of the phase inversion stage 10, the output of which is connected to the constant current source 1. The output of the monostable flip-flop 13 is connected to the first input of a second

  NAND element 14 and the second entry of NAND element 11.

The output of the INAND element 14, the second input of which receives a switching voltage Us, is connected to the base of the discharge transistor 3, the emitter of which is connected, on the one hand, to ground via d 'a diode 15 and, on the other

  hand, at a bias voltage -U by a resistor 16.

  The ULy voltage delivered by the current source cons-

  while 1, charges capacitor 2 linearly over time. The charging voltage of the capacitor 2 is amplified and clipped by the limiting amplifier 6 so as to show at the output A1, of the decoupling amplifier 7, the rise slope of the sawtooth pulse or of the triangle-shaped pulse. The charging voltage of capacitor 2 is simultaneously applied to the comparator

  4, for the evaluation of the zero crossing, and for the comparison

  5 for the evaluation of the maximum amplitude. When

  presence of a maximum amplitude and in the position shown

  felt from switch 12, comparator 5 closes the circuit

determined on the discharge transistor 3, the monostatic flip-flop

  ble 13 and the NAND element 14 so that the capacitor 2 discharges. Capacitor 2 is charged again as soon as

  the monostable rocker 13 returns to its rest state. The ten-

  Reference frequency Uref determines the amplitude of the sawtooth pulse present at output A1. The amplitude of the charge voltage UL determines the speed of the rise of the sawtooth pulse. One can act on the intervals of the pulse trains via the holding time of the monostable rocker by varying the time constant. The discharge transistor 3 has a slightly negative bias due to the voltage -U so that the capacitor 2 is also charged by

a negative voltage when the transistor 3 is on.

  The limiting amplifier 6, having very precise thresholds, limits the negative input voltages exactly to 0 Volt and thus always creates a defined and constant interval for the trains of pulses. This value of the intervals is also obtained when the generator is switched off by blocking the switching voltage US, the NAND element 14 and by switching on the discharge transistor 3. The beginning and the end of the sawtooth pulses are determined by the comparators 4, 5. A rectangular pulse-having a switching flank at the beginning and at the end of the sawtooth appears synchronously with the sawtooth pulse at the output A2 of the element NA1D 11. This rectangular synchronous tension with the saw teeth is for example necessary when one wants to obtain suppression pulses for a display unit connected to the generator. The position of the sawtooth pulse can be offset from the zero line using the variable offset voltage Uv which represents a reference voltage for the decoupling amplifier. When Uv is zero, the start state or the quiescent state coincides with the zero line. When Uv is equal to Uref the impulse

  in the shape of a sawtooth is symmetrical with respect to the line

gne zero.

The switch 12 allows., By simple means,

  using the generator for triangular functions

res. In this case the capacitor 2 is not switched on

  by transistor 3 when the curve reaches its maximum.

The transistor 3 is only switched on by the voltage

  switch to stop the generator. When the im-

  pulse reaches maximum amplitude, pulse is de-

  delivered, via comparator 5, to the information stage

  phase 10 version acting as a sign reverser

so that the polarity of the UL charging voltage is

  paid. In this way the capacitor 2 is charged by a constant current of reverse polarity. When the pulse has reached its minimum, the comparator 4 delivers a pulse to the phase inversion stage 10, which has the effect of

  further change of polarity of UL charging voltage.

  This process is repeated and at output 1, triangular pulses appear, whose characteristic values and the position relative to the zero point can be adjusted,

as already mentioned, by varying the tensions. The va-

  their pulse characteristics can be adjusted

  individually without interaction but they can also

be modified by an electronic calculator.

Claims (2)

R E V E N D I C A T I O N S 1. Switchable generator delivering pulses   in the shape of a sawtooth and in the shape of a triangle and   both a constant current source to which a capacitor is connected and a discharge transistor which is connected in parallel to this capacitor, characterized in that the output of the constant current source (1) is connected, on the one hand, with each of the inputs of two compa- rateurs (4, 5) and, on the other hand, through a limiting amplifier (6), with the first input of a decoupling amplifier (7) whose second input receives a variable control voltage ( Uv) as offset voltage, in that the output of the first comparison   tor (5), the second input of which is connected to a voltage reference sion (U ref), is optionally connected by a switch (12), either to the input of a monostable rocker (13), or to a first input of a phase inversion stage (10 ), in that the output of the second comparator (4), the second input of which is at zero potential, is connected to the first input of a NAND element (11) to function   NAND to decouple a rectangular pulse chrone, and at the second input of the phase inversion stage (10), the third input of which receives a charging voltage (UL) for the capacitor (2) and the output of which is connected to the input of the constant current source (1), and in that the output of the monostable rocker (13) is connected, on the one hand, to the second input of the NAND element (11) and, on the other hand, by l 'through a gate, which can be blocked, at the control input of the discharge transistor (3) which is polarized in opposition to the charge voltage of the capacitor (2).   2. Generator according to claim 1, characterized in that the charging voltage, the switching voltage of the lockable door, the offset voltage and the voltage   are controlled by an electronic calculator than.