US2163214A

US2163214A - Relaxation oscillation generator

Info

Publication number: US2163214A
Application number: US739301A
Authority: US
Inventors: Schlesinger Kurt
Original assignee: Loewe Opta GmbH
Current assignee: Loewe Opta GmbH
Priority date: 1933-08-14
Filing date: 1934-08-10
Publication date: 1939-06-20
Anticipated expiration: 1956-06-20
Also published as: FR777151A; GB442740A; NL45863C

Description

June 20, 1939. SCHLEQNGER I 2,163,214

RELAXATION OSCILLATION GENERATOR Filed Aug. 10, 1954 Patented June 20, 1939 UNITED STATES RELAXATION OSCILLATION GENERATOR Kurt Schlesinger, Berlin, Germany, assignor to Radioaktiengesellschaft D. S. Loewe, Berlin- Steglitz, Germany Application August 10,

1934, Serial No. 739,301

In Germany August 14, 1933 3 Claims.

The present invention relates to relaxation oscillation generators in television apparatus, including a gas-filled, grid-controlled, thermionic tube, for producing line and frame deflecting voltages.

In the working of such apparatus as heretofore used several inconveniences occur which are got rid of in an arrangement according to the present invention.

One object of the invention is to provide means to give the discharge a definite duration, which allows the discharge accurately to be governed, and to accelerate at the same time the break-down of the deflecting voltage after ignition.

Another object of the invention is to provide means for compensating a deviation of the straight line form of the deflecting voltage.

A further object of the invention is to avoid interferences which may be caused by reaction of the amplifier to the discharge tube or of one of the two generators to the other one.

A further object of the invention is to avoid grid currents in the discharge tube when it is in the state of ignition.

According to still a further feature of the invention, the grid bias of the discharge tube is taken from the anode Voltage supply in such a manner as to compensate fluctuations in the said supply with regard to the influence exerted on the ignition moment.

The invention will be. more fully understood by reference to the following detailed description in connection with the appended drawing, which shows diagrammatically a generator for producing deflecting voltages according to the present invention.

In the drawing, I is the gas-filled thermionic tube, 2 the storage condenser, 3 the charging resistance and 5 the indirectly heated cathode of the tube, which is positively biassed in relation to the grid by means of the adjustable resistance 4. Since resistance 4 is fed by the anode potential, the grid bias undergoes all fluctuations of this potential so that a shifting of the ignition moment by these fluctuations is safely avoided. The charging potential is fed in through steadying means 2I, 22.

The control potentials are supplied to the grid of the tube I by the terminal 6 via a condenser O 24. The anode I of the tube I is connected via the coupling condenser with the control grid 8 of the screen grid amplifier tube 9. Thecontrol grid bias is fed in at IT via steadying means 32, and the grid resistance. The bias of the screen grid I0 is tapped at the potentiometer II in such manner that the commencing exponential curvature of the circuit charging the condenser 2 and consequently of the deflecting voltage is compensated by the opposite curvature in the characteristic of the tube 9. Remaining distortions of the straight line form of the deflecting voltage may be compensated by a high-pass filter consisting of condenser 25 and ohmic resistance 28 connected in parallel, and inserted in the lead coupling both tubes. The working point on the characteristic is, by suitably biassing the control grid, made to be situated in the lower bend. From the anode I8 of the amplifier tube the amplified relaxation oscillation voltage potential (i. e. the potential drop across the anode resistance) is coupled by the condenser I3 to the potentiometer I 4 which permits fine adjustment of the image size. The tap of this potentiometer is connected to the terminal I5, which may be connected directly with the deflecting system of the Braun tube.

In the case of a tube I having cathodes of high emission, the condenser 2 discharges in such a short time (about 1 micro-sec.) that the ionisation does not disappear after quenching sufficiently quickly, at least not in the line deflection tube. In this case irregularities occur in the ignitions of the tube, so that a disquietude appears over the entire image in a horizontal direction.

It has been found that this disquietude disappears entirely if the emission of the tube I is suitably reduced. This method, however, is by certain reasons unsuitable in practice.

A satisfactory remedy against the irregularities in the initiation of discharge has been found in the use of a resistance I9 inserted in the discharge circuit of the tube I. The resistance I9 is 100 ohms, with a capacity 2 of 2.10 mf., so that the duration of the discharge is at least equal to or greater than the period of transmission ofan image point, the time constant of the discharge circuit being approximately 2 micro-sec.

It is important to connect the amplifier 9 with the anode of the tube I and not with the condenser 2 directly. This has the effect that, because in the moment of ignition the potential on the tube I drops much quicker than that on the condenser, the cathode ray returns instantaneously without to produce a visible line on the screen.

According to a further feature of the invention a resistance 20 of the order of several ten-thousands ohms is provided in the lead to the grid of tube I, which safely prevents the main discharge arc, anode-cathode from partially flashing over to the grid and thereby causing an uncontrollably and unsteady leak current to flow. This measure is not so necessary to be taken in the line frequency as in the frame frequency oscillator.

Further, according to the invention the anode circuits of both amplifiers are, as a whole, carefully screened off against the respective amplifier control grid circuits, taken as a whole, as indicated by the dotted line 30.

Furthermore, according to the invention, the line frequency arrangement and the frame-frequency arrangement are prevented from exerting any influence on the working of each other by carefully screening-0E them against each other and by providing separate steadying means 32, 35 for the control grid bias of the two amplifiers.

The amplifier tube 9 of the line-frequency arrangement is, according to the invention, silvered on the inside and the silver coating passed to earth to prevent capacitative retroaction from being exerted by the amplified oscillations on the grid circuit of the discharge tube I, which Would cause a shifting of the ignition point. A silver coating of this nature in the amplifier tube of the frame-frequency arrangement may be dispensed with because of the lower frequencies.

The single elements, for the production of a 180-line pattern, may be selected as follows:

Resistances Line frequency Frame frequency 3 1.2.megohms. 4 3,000 ohms 3,000 ohms. l'1 10" ohms 10 ohms. 12 100.000 ohms, 14 Not higher than 100,000 Not higher than 100,000

ohms. ohms. 100 ohms 30,000 ohms.

.1 inegohm. .5 megohm. 1 megohm. .1 megohm.

1 megohms- 0.1 megohm. 60,000 ohms Condensers Line irequency- Frame frequency plifier being coupled by a secondcondenser to the common terminal of the first circuit and anode of said tube.

2. In a device according to claim 1, in which said circuit means. includes a grounded point and a biasing resistance between said cathode and said grounded point.

3. In a device according to claim 1 having filtering elements in said second mentioned circuit.

KURT SCHLESINGER.