DE1223877B - Saw tooth generator - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

H03k

German class: 21 al - 36/02

Number: 1 223 877

File number: M 62866 VIII a / 21 al

Filing date: October 23, 1964

Opening day: September 1, 1966

The invention relates to a sawtooth generator for generating a sawtooth-shaped voltage, which has a long trace time, but a short return time and good linearity.

In the case of a sawtooth voltage with a long trace time on the order of 100 seconds and more, it is difficult to obtain a short flyback time and good linearity of the sawtooth voltage. Known circuits for generating sawtooth-shaped voltages are the Miller integrator, the so-called bootstrap circuit, and relaxation oscillator circuits in which a capacitance is charged by a source of constant current. Such circuits are satisfactory in generating sawtooth voltages of relatively short periods. In order to generate voltages with a long period, however, it is necessary to use capacitors with a large capacity, which increases as the period duration of the sawtooth voltage increases. Such large capacitors, however, have large leakage currents, which cause poor linearity in the voltage generated. In addition, since the switching elements used to discharge the capacitor can only process a limited current in such circuits, there are limits to the ratio of the delay time to the delay time. With a long run-down time, ie large capacitors, a short run-down time is practically impossible to achieve. The invention is based on the object of avoiding these difficulties. The invention makes it possible to achieve ^{ramp-down times in the order of magnitude of 10 ~ 4} seconds and good linearity of the sawtooth-shaped voltage with a trajectory time in the order of magnitude of 10 ^{3 seconds.}

The invention consists in a generator for a sawtooth voltage of a particularly long period in that first a staircase voltage is generated, the amplitude of which varies during the long Period duration changes in uniform steps, and that this staircase voltage by adding a sawtooth-shaped auxiliary voltage with the period and the amplitude of a step is added to the desired sawtooth voltage.

It is known ("Electronics", 1957, p. 167), by combining a first sawtooth voltage to gain a staircase voltage with a second, higher frequency sawtooth voltage. This However, the circuit is not based on the task of generating a sawtooth voltage with a particularly long period to create. Also here is not used to generate a sawtooth generator

Applicant:

Marconi Instruments Limited, London

Representative:

Dr.-Ing. B. Johannesson, patent attorney,

Hanover, Göttinger Chaussee 76

Named as inventor:

John Francis Fulford, St. Albans, Hertfordshire

(Great Britain)

Claimed priority:

Great Britain October 24, 1963 (41 966),
dated September 23, 1964

A sawtooth voltage initially generates a staircase voltage, which is then increased by a higher frequency Sawtooth voltage is supplemented to a sawtooth voltage with a long period.

The sawtooth-shaped auxiliary voltage is referred to below as a sawtooth voltage with a short period designated.

The two voltages mentioned are preferably added in an adding network, with Means are provided with which the amplitudes of the two voltages can be changed in opposite directions are, so that after appropriate adjustment, the amplitude of the sawtooth voltage of a short period the amplitude of the individual steps of the staircase voltage is the same.

In one embodiment of the invention, the two combined voltages, d. H. the staircase voltage and the short period sawtooth voltage, as soon as they are generated same amplitude.

The staircase voltage is preferably generated by a digital staircase voltage generator, which is controlled by pulses from a generator, which is also the generator for the sawtooth voltage short period controls. The said generator for generating the sawtooth voltage short period preferably contains a capacitor, a source charging the capacitor

609 658/369

3 4

approximately constant current as well as one through the The circuit according to FIG. 1 generated according to FIG. 2a

Pulse generator controlled circuit for discharging at the output of the adder 6 a stair span

of the capacitor. tion 10, where the period of a stage, d. H.

The period duration and / or the slope of the width of a step is given by the period sawtooth voltage generated according to the invention longer 5 of the control pulses 13 from the pulse generator 1, and Periods can thereby be made adjustable, although the period duration of a stair step is the same that the staircase voltage generator and at the same time the period of the control pulses 13 at the Ausder Generator for the sawtooth voltage short run of the pulse generator 1. At the "hot" end of the Period can be set, with all setting capacitors 3 a sawtooth voltage 11 is achieved the sum of the two voltages of both the short period measured in FIG. 2b and the connection Generators a sawtooth voltage approach the output of the isolation amplifier 7 is supplied. The Pelinearic Islands And a long period. If the period of this sawtooth voltage is short period the pulse generator at the same time the digital staircase is equal to the period of one stage of the staircase voltage generator and the discharge of the capacitor 10, and the amplitude of the sawtooth capacitor causes the voltage in the generator to 15 is equal to the difference in amplitude Generation of the sawtooth voltage with a short period between two steps in the stairway span and from a constant current source 10.

is charged, the frequency of the pulse can It is also possible that the amplitude of the Sägegenerators and with adjustable a control circuit tooth voltage be 11 not coupled is equal to the amplitude · ', which is the output voltage of the source _ao difference between two steps of the staircase voltage 10 constant current influenced. But then the adder 8 is set so that

The invention is described below on the basis of the addition of the two supplied span * Drawings on an exemplary embodiment in more detail, the amplitudes of the effectively put together, th voltages 10 and 11 are again the same size,

1 shows a block diagram of the invention, 35 the two voltages 10 and 11 according to FIG. 2a

while in and 2b result 'after they have been put together in

F i g. 2 curves to explain the we-adding stage 8 a sawtooth voltage 12. longer

k manner of the circuit according to FIG. 1 period shown in FIG. 2 c, which has good linearity and

are; has a particularly short return time. .

Fig. 2a shows the staircase voltage generated, 30 The sawtooth voltage 11 is used for a short period

Fig. 2b shows the sawtooth voltage of a short period in addition to the individual steps of the stairs:

and voltage 10 "fill up". The ratio of

2c shows the sawtooth voltage with a long period, the period duration of the sawtooth voltage 12 with a longer period

and short ramp-down time, which by adding the period to the "fill-up voltage 11" can be

Stresses according to FIGS. 2a and 2b arise. 35 can be made large by using a corresponding

In the illustrated embodiment, the corresponding number of steps is in the staircase voltage

Slope of the sawtooth voltage long period Ί0 is chosen. If, as in the one shown

positive, d. That is, the voltage increases in its amplification exemplary embodiment, the staircase voltage generation

tude over time. The invention is of course tor 5 is a digital circuit arrangement is that

also applicable for the generation of a sawtooth 40 number of steps generally a multiple of

long period and negative two. With appropriate readjustment pulses can

Pitch. but in a known way also another number of

Fig. 1 shows a pulse generator whose fre-stair steps are achieved. For example, ent sequence, as shown by the arrow, can be set. The circuit also contains a source of 2 an- 45 512 (2 ⁹ ) steps and a "fill-up voltage" with an approximately constant current of a known type. Before a period of 5 seconds a sawtooth pattern, the value of the constant current at the voltage with a long period of 2560 seconds output of source 2, as indicated by the arrow, is adjustable despite the great length of this period. The means for setting the pulse generator duration, the return time of the emerging output port 1 and the source 2, are coupled to one another, voltage in the order of magnitude of the return time as indicated by the dash-dotted line. the "fill-up voltage" is. Since the period

The current from source 2 charges approximately linearly this "filling voltage" is only 5 seconds,

a capacitor 3 on which has a discharge ^ so it is not difficult to have a flyback time in the

circuit 4 can be discharged. To achieve the discharge scarf order of 10 ~ ^{4 seconds,}

tang 4 is controlled by control pulses 13 from the pulse 55 The period duration of the staircase voltage 10 can

generator 1 controlled. by changing the pulse frequency of the control

The control pulses 13 are also changed by a starting pulse 13 from the pulse generator 1. Order 5 is fed with binary circuits whose To maintain linearity in the sawtooth chip outputs connected to a summing circuit 6 12 with a long period duration becomes ones in the case of one are, from the supplied input voltage settings 60 whose period the slope of the »padding a staircase voltage 10 generated, voltage 11 ″ also set so that this

The “hot” end of the capacitor 3 is always the staircase voltage 10 at the “filling voltage” Input of an isolation amplifier 7 connected. Which is filling up. To have a large adjustment range for Output voltages of the adder 6 and the frequency of the output voltage 12 to be educated isolation amplifier 7 are 8 65 len in an adding step, the number of steps in the staircase put together, the voltage 10 at an output terminal 9 adjustable to different values the desired sawtooth voltage 12 be long period, so that with a relatively small supply, the frequency of the control pulses 13 and the rich

. 6th

Sawtooth voltage 11 a large frequency range for the generated sawtooth voltage 12 can be achieved can.

Claims (7)

Patent claims: 1. Generator for a sawtooth voltage of a particularly long period, characterized in that that first a staircase voltage (10) is generated, the amplitude of which is uniform during the long period Steps changes, and that this stair voltage (10) by adding a sawtooth-shaped Auxiliary voltage (11) with the period and the amplitude of a stair step the desired sawtooth voltage (12) is added. 2. Generator according to claim 1, characterized in that the amplitudes in one Adding stage (8) composite staircase voltage (10) and the auxiliary voltage (11) in opposite directions are changeable. 3. Generator according to claim 1, characterized in that the staircase voltage (10) is generated by a digital staircase voltage generator (5) which is controlled by pulses (13) of a pulse generator (1) which simultaneously controls the auxiliary sspaanungsgenerator (2, 3, 4) will. 4. Generator according to claim 3, characterized in that the auxiliary voltage generator contains a capacitor (3) and a source (2) of constant current connected to it, and that the capacitor (3) is controlled by a circuit controlled by the pulse generator (1) (4) is discharged. 5. Generator according to claim 1, characterized in that to change the period duration and / or amplitude of the sawtooth voltage (12) of a long period of the staircase voltage generator (5) and the auxiliary voltage generator (2, 3, 4) can be set at the same time so that the sum of the voltages for each setting (10, 11) of the two generators gives the desired sawtooth voltage (12). 6. Generator according to claim 3 and 5, characterized in that the frequency of the pulse generator (1) and the output voltage of the source (2) of constant current adjustable in synchronism are. 7. Generator according to claim 1, characterized in that the period duration of a stair step is small compared to the long period of the desired sawtooth voltage (12). Considered publications:
"Electronics", 1957, No. 6, pp. 167 and 168. 1 sheet of drawings 609 658/369 8.66 © Bundesdruckerei Berlin